72 results about "Symmetrical components" patented technology

Capacity-optimized grid-forming is provided. A controller includes a power-synchronization model (PSM). The PSM is configured to receive positive and negative sequence symmetrical components of an output voltage and an output current. The PSM is configured to generate current references including a positive and negative sequence current reference. The PSM is configured to generate an internal voltage phase reference and voltage magnitude reference. The controller includes a capacity constrainer to determine, based on the current references and a capacity limit terms, that a device is capacity constrained. The capacity constrainer is configured to determine optimum complex gains to scale the plurality of current references based on the capacity limit terms. The capacity constrainer is configured to, responsive to the determination of constraint, output scaled current reference to cause a power stage to adjust the output voltage / current, the scaled current reference scaled according to the complex gains.

The invention discloses an open-phase detection method and device suitable for a system with multiple starting standby transformers. The method comprises the following steps: measuring a three-phase current on an incoming line, measuring a neutral point zero sequence voltage of each starting standby transformer, and collecting a neutral point grounding knife switch position of each starting standby transformer; based on the three-phase current on the incoming line, calculating an incoming line positive sequence current and an incoming line zero sequence current by using a symmetric component method; and according to the incoming line zero-sequence current, the neutral point zero-sequence voltage of each starting standby transformer and the position of a neutral point grounding knife switch, judging whether an open-phase fault occurs and positioning a fault interval. The method is suitable for a parallel connection mode of a plurality of starting and standby transformers, is also suitable for a transformer neutral point grounding or non-grounding system, and can effectively identify open-phase faults on a high-voltage side and a line of the starting and standby transformer under no-load and light-load working conditions.

The invention provides a self-networking control protection method and device for a grid-connected energy storage converter, and a medium. The method comprises the following steps: acquiring electrical quantities of a grid-connected point and a direct current side, establishing a short-circuit capacity estimation value and a positive and negative zero sequence model, and generating a voltage phasor reference; generating a given frequency and a given voltage according to the power and frequency droop and the reactive power and voltage droop; generalized impedance shaping is executed in a control loop, and virtual impedance and selective filtering are configured according to frequency bands; completing grid connection or re-connection according to a sequence of frequency slope, phase angle slow alignment and voltage amplitude gradual combination based on a grid connection point reference phasor; setting positive-sequence, negative-sequence and zero-sequence fault current upper limits and a time sequence template in the symmetric component domain; and outputting the given frequency, the given voltage, the sequence component limit value and the protection state instruction to a converter power bridge driving and grid-connected switch control interface. According to the invention, phase-lock-free grid-connected synchronization, unified control protection switching, sequence component controlled fault current and weak grid stable operation can be realized.

The invention discloses a DG-containing distribution line single-phase earth fault single-end impedance distance measurement method and system, and the method comprises the steps: inputting parameters and DG distribution conditions into equipment, when a distribution network has a single-phase earth fault, enabling the zero-sequence voltage of the equipment to rise, judging the occurrence of the single-phase earth fault, and starting fault distance measurement calculation; using a symmetric component method to calculate sequence components of voltage and current at the bus, the DG access, the load access and the fault point; and on the basis of the sequence components of the voltage and the current of the fault point, the phasor angle difference between the voltage and the current of the line fault is obtained, and the fault distance is calculated according to the phasor angle difference. The method is good in distance measurement effect and has practicability.

The invention discloses a distributed photovoltaic access power distribution network pilot direction protection method, device and equipment and a storage medium, and relates to the field of power system relay protection. The method comprises the following steps: synchronously acquiring discrete signals of three-phase voltage and current of a main grid side and a photovoltaic side based on N points of each cycle; performing data processing: performing real-time calculation on the acquired voltage and current signals by adopting Fourier transform and a symmetric component method to obtain a main grid side positive sequence voltage, a photovoltaic side positive sequence voltage, a main grid side positive sequence current and a photovoltaic side positive sequence current; generating a double-criterion logic of a voltage criterion and a current criterion based on the obtained calculation result; and when the voltage criterion and the current criterion meet the internal fault condition at the same time and n cycles are continuously maintained, triggering the tripping action of the protection device. The method has the beneficial effects that the internal / external faults are effectively distinguished through the significant difference of the current amplitude ratio of the main grid side and the photovoltaic side, and the problem that the protection sensitivity is reduced due to photovoltaic access is solved.

The invention discloses a power supply system impedance and short-circuit current detection method and system, and relates to the field of electrical variable measurement, in the method, node voltage and current characteristic quantities are calculated based on collected data, a voltage drop equation is established, line impedance is calculated, and impedance correction is performed by considering temperature influence. Obtaining parameters of the transformation equipment, determining impedance of the transformation equipment and calculating load equivalent impedance. A short-circuit fault is identified by monitoring a current change rate, a voltage amplitude and a high-frequency characteristic in real time and combining a judgment threshold value set by historical data. And after the occurrence of the short-circuit fault is judged, the fundamental wave short-circuit current is calculated by using the corrected impedances and a symmetric component method, and the peak value of the short-circuit current is finally obtained by combining the impact coefficient calculated by the ratio of the real-time reactance to the resistance of the system. The method and the device are used for improving the accuracy of a short-circuit current calculation result in an environment with dramatic temperature change, so that the reliability of relay protection setting is improved.

A kind of single-phase grounding fault single-end impedance ranging method and system of DG-containing distribution line, method includes: input parameter and DG distribution to equipment, when single-phase grounding fault occurs in distribution network, the zero sequence voltage of equipment rises, it is judged that single-phase grounding fault occurs, and fault ranging calculation is started;Using symmetrical component method to obtain the sequence components of voltage and current at bus, DG access, load access and fault point;On the basis of the sequence components of voltage and current at fault point, the phase angle difference between line fault phase voltage and current is obtained, and the fault distance is calculated according to the phase angle difference.The ranging effect of the method of the application is very good, and it has practicality.

The invention relates to the field of magnetic suspension motor driving control, and discloses a high-reliability motor commutation method based on same-frequency displacement conversion of a magnetic suspension rotor, and the method comprises the following steps: collecting a multi-channel rotor displacement signal of a magnetic suspension bearing system; carrying out same-frequency positive-sequence component extraction and phase locking calculation to obtain a rotor space angle position estimation value; multiple paths of redundant rotor angular position signals are constructed, and main rotor space angular position signals are generated; executing initial alignment and error correction of a motor rotor angle, and locking an angle compensation value in a closed loop mode based on the waveform change rate of the direct current bus current at the pre-estimated commutation moment; synthesizing the motor commutation angle, and generating a pulse width modulation signal to drive the motor to operate. A magnetic suspension rotor displacement signal is processed through a second-order generalized integrator cascade instantaneous symmetric component method, so that the effect of high signal-to-noise ratio rotor position detection is realized by directly utilizing an existing magnetic bearing displacement sensor under the condition that a Hall element or a photoelectric encoder does not need to be additionally arranged.

The invention discloses a five-phase permanent magnet synchronous motor turn-to-turn short circuit fault diagnosis method, and relates to the technical field of multi-phase permanent magnet synchronous motors. Performing symmetric transformation on the phase current according to a symmetric component method to obtain a first positive-sequence component, a first negative-sequence component, a second positive-sequence component and a second negative-sequence component of the current, and performing Fourier transformation on the four current symmetric components to obtain an amplitude and a phase angle of each current symmetric component; and a turn-to-turn short circuit fault diagnosis result of the five-phase permanent magnet synchronous motor can be obtained according to the amplitudes and phase angles of the four current symmetrical components. According to the method, early turn-to-turn short circuit fault diagnosis can be realized by using current symmetric components by adopting a signal analysis method, and the reliability and the accuracy of online diagnosis are improved.

A phasor measurement unit (PMU) of the present disclosure measures phasor, i.e., magnitude and phase angle of voltage and current, and related data from a specific location on the electrical gird synchronized to a common time source. The time-synchronized phasor is called a synchrophasor. In a system of the present disclosure, a plurality of PMUs transmit the synchrophasors and related data to a phasor data concentrator (PDC), which aggregates and time-aligns the data for real time and post analysis. The PMU of the present disclosure further functions as a power quality meter determining at least one of symmetrical components' phasor, frequency, rate of change of frequency, high-speed digital inputs, analog fundamental power and / or displacement power factor.

The invention belongs to the technical field of transient analysis of a new energy grid-connected system, and particularly relates to a transient overvoltage analysis method of a direct-driven wind power grid-connected system under an asymmetric fault, which comprises the following steps: acquiring three-phase asymmetric voltage and current, and constructing a positive and negative sequence dq control model of positive and negative sequence bisynchronization of a direct-driven wind power plant station; establishing a mapping relation with a symmetric component method, and determining a positive-sequence dynamic reactive current increment and a negative-sequence current suppression coefficient according to a converter control strategy; establishing sequence network boundary conditions under various asymmetric faults; enabling the direct-driven wind power plant to be equivalent to a frequency-related controlled sequence impedance source, and obtaining equivalent sequence impedance of the wind power plant; establishing a sequence network equation considering wind power dynamic support; calculating the current and sequence voltage of the fault point, and obtaining a three-phase voltage through symmetric component inverse transformation; and an overvoltage coefficient is calculated, and a quantitative relational expression between the overvoltage coefficient and the negative-sequence current suppression coefficient is established and applied. The method provides theoretical support for parameter setting and capacity planning of the wind power integration system.

The application provides a unified and cooperative control method and system for power and current of a grid-connected converter under an unbalanced grid condition, an electronic device and a storage medium. It belongs to the field of renewable energy power generation. The method comprises the following steps: obtaining output AC and DC power and grid voltage of the converter; calculating active and reactive power based on the output voltage and current; calculating reference voltage phase angle and amplitude through active-frequency and reactive-voltage control; calculating virtual current through virtual impedance by using the reference voltage and the grid voltage; calculating virtual power by combining the output voltage; calculating reference current containing harmonics through instantaneous power inverse transformation based on the virtual power; generating the final adjustable reference current through harmonic extraction and adjustment factor adjustment, and performing tracking control. The application does not require instantaneous symmetrical component transformation, does not require positive and negative sequence separation, has no calculation delay, can effectively suppress the harmonic current injected into the grid, realizes flexible and cooperative control of current balance and power constancy of the converter, and improves grid-connected power quality.

The invention discloses a short-circuit current calculation method based on a power frequency model, and belongs to the technical field of power system analysis. The method comprises the following steps: collecting basic parameters of a power system under power frequency, wherein the basic parameters comprise system rated voltage, impedance parameters of each element and a system topological structure; constructing a power frequency equivalent model of the power system based on the power frequency parameters, and forming equivalent circuit representation; determining the type and position of a short-circuit fault; based on a power frequency equivalent model, a short-circuit current value is calculated through a circuit analysis technology, an asymmetric fault is processed by adopting a symmetric component method, and the influence of transition resistance can be considered; and outputting a short-circuit current calculation result for system protection or equipment verification. According to the method, the calculation process is simplified, the calculation efficiency is improved, the calculation precision under the power frequency is ensured, and the method has high engineering practical value.

The invention relates to the technical field of power fault detection, in particular to a fault location method, device and equipment based on fault point injection current, a medium and a program product. The method comprises the following steps: acquiring detection data of a target power transmission line; symmetrical component transformation is carried out on the three-phase voltage measurement value and the three-phase current measurement value of the source end and the receiving end, and current components of the source end and the receiving end are obtained through decomposition; constructing a uniform transmission line equation matched with the target transmission line, and constructing a distributed line model corresponding to the target transmission line based on the detection data; constructing a fault current criterion function based on the distributed line model; and traversing and calculating the value of the fault current criterion function between the source end and the receiving end of the target power transmission line, and positioning to obtain the target fault point. By adopting the method, the accuracy of a positioning result can be improved.

The application discloses a kind of power supply system impedance and short-circuit current detection method and system, it is related to the field of measurement electric variable, in the method, by calculating the node voltage and current characteristic quantity based on the data collected, line impedance is calculated by establishing voltage drop equation and considering temperature influence impedance correction is carried out.The impedance of transformer equipment is determined by obtaining the parameters of the transformer equipment, and the equivalent impedance of the load is calculated.The short-circuit fault is identified by real-time monitoring of the current change rate, voltage amplitude and high-frequency characteristics, and the threshold set by historical data is combined to identify the short-circuit fault.After determining that a short-circuit fault occurs, the fundamental short-circuit current is calculated using the modified impedances by the symmetrical component method, and the impact coefficient is calculated by combining the real-time reactance and resistance ratio of the system, and the peak short-circuit current is finally obtained.The application is used to improve the accuracy of short-circuit current calculation results in a temperature environment with large fluctuations, thereby improving the reliability of relay protection setting.

The application discloses a kind of based on currentless sampling area end voltage monitoring and collaborative control method and system, comprising: by parallelly arranged in low-voltage distribution area end voltage monitoring device, real-time acquisition area end three-phase voltage instantaneous signal;According to three-phase voltage instantaneous signal extraction fundamental voltage complex phasor;Fundamental voltage complex phasor is carried out symmetrical component transformation, obtains positive sequence voltage component and negative sequence voltage component;According to positive sequence voltage component and negative sequence voltage component, generate comprehensive state index;According to comprehensive state index, generate target compensation voltage complex phasor including positive sequence control amount and negative sequence compensation amount;According to target compensation voltage complex phasor, by parallelly connected control device that accesses area end, injects compensation current to area end.This application aims at solving prior art in dependence on current transformer leads to installation complex, there is power failure construction risk;Voltage, overvoltage and three-phase unbalance problem scattered management, lack unified processing framework;Voltage monitoring and control are independent of each other, cannot form collaborative closed loop and other problems, realize without dependence on current transformer installation, can unifiedly process various voltage problems, and make voltage monitoring and control form collaborative closed loop.

The invention relates to a system and method for monitoring motor winding degradation. Systems (100) and methods are provided for monitoring motor winding degradation of an electric machine having an electric motor (106) driven by a variable speed drive (VSD) (102). A sensor of the VSD (102) detects a measurement of the phase current and / or phase voltage while driving the electric motor (106). Each measurement value (114) is processed using a filtering module (116) to calculate a symmetric component (118). The resulting symmetric component (118) is used to identify a motor winding state (120) of one or more motor windings.

The invention discloses a medium-voltage cable fault section rapid positioning method and system equipment based on moving average filtering and instantaneous symmetric component analysis, and a storage medium, and the method effectively weakens high-frequency noise through carrying out moving average filtering processing on collected three-phase current signals, and then carries out the rapid positioning of a fault section of a medium-voltage cable based on an improved instantaneous symmetric component method. Extracting positive-sequence and negative-sequence current components in real time, and judging the position of a fault section through the direction change; the method has good robustness and real-time performance.

Proposed is a method for assembling non-rotatably interconnected components (2, 3) of a bearing assembly (1), comprising the following steps: - providing two rotationally symmetrical components (2, 3), namely a bearing ring (3) and an attachment component (2) to be connected thereto, wherein one of the two components (2, 3) has an annularly encircling depression (12, 15) on a surface facing toward the other component (3, 2), - filling the annularly encircling depression (12, 15) with an elastomer, and - pushing the two components (2, 3) together, wherein the component (2, 3) into which the elastomer was introduced provides a metal guide surface (4, 11) which adjoins the elastomer in the axial direction of the component (2, 3) in question, and wherein a metal surface (11, 4) of the second component (3, 2) is pushed beyond the guide surface (4, 11) until said metal surface (11, 4) lies force-transmittingly on the elastomer and is spaced in the axial direction from the guide surface (4, 11).

The invention discloses a power grid adaptive direction distance protection method and system based on an apparent power supply, and the method comprises the steps: building a home terminal dynamic equivalent apparent power supply model based on a voltage phasor and a current phasor obtained through measurement at a protection installation part, and enabling the model to be defined by two key parameters, namely, an apparent power supply voltage amplitude and equivalent impedance; three-phase voltage and three-phase current at a protection installation position are collected in real time, positive sequence voltage is calculated through a symmetrical component method, and the real-time phase difference between the dynamic equivalent apparent power source at the terminal and the three-phase voltage and the three-phase current is calculated; comparing the real-time phase difference with a preset action interval; when the real-time phase difference is in a set action interval, judging that a fault is a forward fault, and starting a protection action; and otherwise, a reverse fault is determined, and latching protection output is carried out. According to the method, the dependence of traditional protection on fixed source impedance parameters is effectively overcome, multiple control strategies such as unit power factor control, low voltage ride through and negative sequence current suppression of the wind turbine generator are adaptively compatible, and the interference of harmonic waves and power fluctuation on protection is remarkably suppressed.

The application provides a grid-connected friendly energy storage converter self-networking control protection method, device and medium. The method comprises the following steps: collecting electrical quantities of a grid-connected point and a direct current side, establishing a short-circuit capacity estimation value and a positive and negative zero sequence model, and generating a voltage phasor reference; generating a frequency given value and a voltage given value according to power and frequency droop and reactive power and voltage droop; performing generalized impedance shaping in a control loop, configuring virtual impedance and selective filtering according to frequency bands; completing grid connection or reconnection according to the order of frequency slope, phase angle alignment and voltage amplitude convergence based on the grid-connected point reference phasor; setting positive sequence, negative sequence and zero sequence fault current upper limits and time sequence templates in a symmetrical component domain; and outputting the frequency given value, the voltage given value, the sequence component limit value and the protection state instruction to a converter power bridge drive and a grid-connected switch control interface. The application can realize no-phase-lock grid connection synchronization, unified control protection switching, sequence component controlled fault current and weak grid stable operation.

This invention discloses a novel method and system for actively sensing the operating status of a power distribution system. The method includes: identifying multiple monitoring points in the power distribution system; actively injecting a power frequency signal into the neutral point and simultaneously acquiring the three-phase and zero-sequence electrical quantities at each monitoring point; then decomposing the quantities into positive-sequence, negative-sequence, and composite zero-sequence components using the symmetrical component method; and comparing the composite zero-sequence quantity with the measured zero-sequence quantity to accurately determine whether the monitoring terminal is functioning correctly, thereby identifying reliable diagnostic sections and avoiding misjudgments caused by measurement anomalies. Based on this, the load imbalance is quantified by the ratio of negative-sequence to positive-sequence current at normal monitoring points, providing a direct assessment of the economic efficiency of the power grid operation. Simultaneously, the zero-sequence impedance is calculated using the zero-sequence voltage and current under normal conditions to effectively verify the protection settings of the switching equipment. Finally, a state evaluation equation integrating multiple characteristic quantities is established to output the normal or fault state of the power grid in real time. This method can actively sense the operating status of the power distribution system during normal operation.

The application discloses a kind of multi-loop high-voltage cable fault calculation method, device, electronic equipment and medium.The multi-loop high-voltage cable fault calculation method includes: when the asymmetric ground short circuit of high-voltage cable metal sheath occurs, asymmetric ground short circuit is converted into target symmetric three-phase short circuit by symmetric component method, and the asymmetric ground short circuit includes single-phase ground short circuit and two-phase ground short circuit;Based on the principle of multi-loop high-voltage cable metal sheath circulating current calculation, the target symmetric three-phase short circuit is calculated, the insulation state of high-voltage cable is determined, to calculate the corresponding multi-loop high-voltage cable fault according to the insulation state.This embodiment studies the insulation state of high-voltage cable line, anticipates high-voltage cable insulation state and takes corresponding measures, which is beneficial to the safety and reliability of high-voltage cable transmission line.

The present invention discloses an optimized operation method and system for a distribution system based on the loss of sensitive equipment, which relates to the technical field of power system optimization. The method includes: analyzing the outage conditions of sensitive equipment based on the symmetrical component method to obtain the cost loss constraints of sensitive equipment; analyzing historical statistical data, obtaining line fault data, and constructing an optimization model with the minimum operation cost of the distribution network as the goal based on the cost loss constraints of sensitive equipment, and constraining the optimization model; building a sensitive equipment grid-connected system in a visualization simulation software to verify the correctness of the optimization model, and using the optimization model to optimize the distribution system. The present invention can effectively prevent the shutdown of sensitive equipment caused by the distribution system operating with faults, and reduce the economic losses of users.

The invention discloses a capacity detection method and device for a distribution transformer, equipment and a storage medium, and relates to the technical field of transformer detection, and the method comprises the steps: carrying out the impedance calculation according to the operation parameters of a to-be-detected distribution transformer based on a symmetric component method, and obtaining the initial zero-sequence impedance of the to-be-detected distribution transformer; performing impedance calculation based on the operation parameters of the to-be-measured distribution transformer, the initial zero-sequence impedance and the depth correction model to obtain target zero-sequence impedance of the to-be-measured distribution transformer; and performing analysis according to the target zero-sequence impedance of the distribution transformer to be detected and the zero-sequence impedance characteristic curve, and determining the actual capacity of the distribution transformer to be detected. According to the method, the actual capacity can be obtained through the operation parameters of the distribution transformer, online verification of the capacity is achieved, the capacity is judged through the zero-sequence impedance of the distribution transformer, the method is not affected by the operation working condition and the environment, the method has wide applicability, the zero-sequence impedance is corrected through the depth correction model, and the accuracy of the detection result is improved.

The present invention discloses a method for calculating the power safety transmission range of a series MMC under AC unbalanced conditions. This method is based on the establishment of a mathematical model of the series MMC under AC unbalanced conditions, and uses the symmetrical component method to analyze the unbalanced voltage at the PCC. It can effectively calculate the positive sequence, negative sequence, and zero sequence voltages at the PCC, and on this basis, analyze the constraint conditions affecting the power safety transmission range. At the same time, the power safety transmission range of the series MMC under AC unbalanced conditions is delineated on the PQ plane, which is helpful for the safe operation of this topology under AC unbalanced conditions. The calculation method has the characteristics of economy, reliability, simple implementation, and excellent performance, and can be applied to the actual project of a flexible DC transmission system adopting a three-phase series MMC.

A method for estimating rotor torques of an aircraft capable of hovering and comprising a plurality of rotors, which are rotatable under the action of respective rotor torques; and an engine, which is operatively connected to the rotors to provide them with an engine torque. Each rotor comprises a hub and a plurality of blades articulated on the respective hub in such a way that respective collective pitch angles are adjustable. The method comprises the steps of i) calculating a symmetric component on the basis of the engine torque; ii) receiving a signal associated with collective pitch angles; iii) calculating an asymmetric component on the basis of a pitch angle difference between the collective pitch angles; and iv) calculating each rotor torque as the algebraic sum of the symmetric component and the respective asymmetric component.

The invention provides a new energy grid-connected system fault protection method based on transient energy characteristics, and the method comprises the following steps: (1), connecting a capacitor in parallel at the tail end of a protected line, and enabling high-frequency signal energy measured at a protection installation part to have significant differences when faults occur inside and outside a region through the bypass effect of the capacitor on high-frequency electrical quantity; (2) taking a current break variable as a starting criterion, and starting protection when the ratio of the measured current to the current before the fault exceeds 1.3 times; (3) carrying out wavelet transformation on the acquired voltage waveform, selecting a db4 wavelet basis, and calculating high and low frequency energy by adopting a wavelet coefficient quadratic sum; (4) judging the ratio of high and low frequency components based on wavelet transform; and (5) on the basis of a symmetric component method, judging a fault phase by detecting whether sequence components exist or not and the amplitude proportion and combining the phase relation of the three phasors, and sending out a corresponding tripping signal to trip off the fault phase. The method can quickly identify the fault of the new energy grid-connected system, and has a certain practical value.

The invention provides a converter access system simulation modeling method, which comprises the following steps of: based on a harmonic frequency spectrum generated when a converter is accessed to a power grid circuit, converting a harmonic signal from a fundamental frequency to the highest number of times into a positive sequence signal, a negative sequence signal and a zero sequence signal under an ABC three-phase static coordinate system through Fourier transform and a symmetric component method; performing DQN coordinate transformation on the positive sequence signal, the negative sequence signal and the zero sequence signal, obtaining six direct current components through Park transformation, and performing combined packaging on the six direct current components to obtain a signal matrix under a DQN coordinate system; establishing a signal operation rule under the DQN coordinate system based on the signal matrix under the DQN coordinate system; and based on a signal operation rule under the DQN coordinate system, constructing a transfer relationship among modules in a power grid circuit, so as to establish a mathematical transfer model of the converter access system under the DQN coordinate system. The precision and the calculation speed of simulation calculation can be improved.

This invention discloses a method for identifying abnormal sampled value data in bus current differential protection, belonging to the field of current abnormal sampled value data identification. It includes three symmetrical component scoring systems (positive-sequence, negative-sequence, and zero-sequence components) and one abnormal sampled data analysis system. The symmetrical component scoring system scores the sampled current amplitude of the bus branch based on its transient and steady-state characteristics and outputs corresponding feature values. The abnormal sampled data analysis system makes a final judgment on whether the sampled current value of the bus differential protection is normal or not based on the output of the symmetrical component scoring system. This invention utilizes the symmetrical component characteristics of the bus branch current to identify abnormal sampled data, and has the advantages of simple implementation, fast identification speed, and high reliability.