152 results about "Harmonic impedance" patented technology

A system-side harmonic impedance estimation method and apparatus, and a storage medium and an electronic device. The method comprises: acquiring an h-th harmonic parameter equivalent circuit simplified on the basis of power grid characteristics, h being a positive integer greater than or equal to 2 (S1); on the basis of the h-th harmonic parameter equivalent circuit, establishing a system-side harmonic impedance estimation mathematical model (S2); acquiring amplitude and phase data of a harmonic voltage and a harmonic current at a PCC (S3); dividing the amplitude data of the harmonic voltage at the PCC into several stable intervals (S4); on the basis of the amplitude and phase data of the harmonic voltage and the harmonic current in the several stable intervals, establishing a variable coefficient regression model between a harmonic voltage phasor and a harmonic current phasor (S5); selecting an optimal window width of a kernel function of the variable coefficient regression model (S6); and calculating a system harmonic impedance on the basis of the variable coefficient regression model and the optimal window width (S7).

The invention relates to the technical field of vehicle charging station operation and maintenance management, and particularly discloses a new energy vehicle charging station operation and maintenance management system and method based on the Internet of Things, and the method comprises the steps: collecting high-frequency harmonic characteristic data in a charging process in real time, and generating harmonic-impedance spectrum combined monitoring data; extracting dynamic attenuation gradient data of the line characteristic impedance; when the dynamic attenuation gradient data is lower than a preset critical safety threshold value, triggering a charging mode switching instruction; the charging piles are controlled to be switched into a charging mode, the phase difference parameters of the multiple charging piles are dynamically optimized, and a phase difference dynamic adjustment instruction set is generated; and finally, self-adaptive correction of the impedance compensation amount is carried out through the MEC equipment, and by self-adaptive correction of the impedance compensation amount, the system can maintain that the overall impedance is constantly greater than a critical safety threshold value, and power loss and equipment damage caused by impedance mismatch are avoided. The real-time feedback mechanism is helpful for improving the energy efficiency of the system, reducing the operation cost and ensuring the long-term reliability of the charging infrastructure.

The invention discloses an active island detection method and system based on harmonic impedance characteristic identification, and the method comprises the steps: analyzing the harmonic impedance difference of grid-connected points in a grid-connected state and an island state, and building a state criterion based on resonant frequency deviation and impedance amplitude through the comparison of the frequency response characteristics of island impedance and grid-connected impedance; fitting the grid impedance into an RLC parallel model in a selected frequency band, and mapping the topological difference of the power grid into a parameter difference; embedding a low-voltage ride-through strategy in the control of the voltage source converter, and adjusting reactive current in a grading manner according to the voltage drop degree of a grid-connected point; fundamental waves and harmonic waves are separated through a cascade notch filter, two synchronous harmonic waves are injected into the system through constant current control, and it is ensured that injection signals of a multi-voltage source converter are in the same phase in a phase locking link; and solving an overdetermined equation set based on the double-frequency response data to identify RLC parameters, setting an island criterion, and synchronously completing island judgment in a low-voltage ride-through time window. Detection precision is improved, dynamic response is optimized, and power generation efficiency is improved.

The invention discloses a reclosing coordination control method and system based on electrical parameter measurement, particularly relates to the technical field of intelligent power grid fault processing and security defense, and is used for solving the problem that the reliability of fault judgment is reduced due to the fact that high-proportion distributed photovoltaic is connected to a power distribution network. A harmonic detection signal is injected during a reclosing waiting period, a response signal is measured, harmonic subspace energy distribution is extracted, an energy distribution matrix is constructed to calculate a nuclear norm change rate and form similarity, a system harmonic impedance stable state is judged through double verification, and finally a reclosing decision is executed according to a fault judgment parameter. The method can accurately identify the convergence characteristic of the dynamic process of the system, effectively distinguish the instantaneous fault from the permanent fault, and significantly improve the reclosing success rate and the power supply reliability of the distributed photovoltaic power distribution network.

The invention discloses a converter harmonic impedance modeling method and related equipment, and belongs to the technical field of converters, firstly, space vectors of voltage and current of a grid-connected point are obtained, the space vectors can accurately reflect the magnitude and direction of the voltage and current in real time, and compared with traditional scalar modeling, more comprehensive information is provided. Based on the space vector, harmonic power under the influence of positive and negative sequence harmonic waves, reference voltage passing through a power control loop and harmonic voltage output by an inverter are obtained through sequential calculation, and modeling of a harmonic impedance model is carried out based on positive sequence harmonic voltage and negative sequence harmonic voltage of an inverter side and a grid-connected point and a power grid main circuit. A harmonic model in a coupling frequency impedance matrix form is adopted, the interaction relation between harmonic voltage and harmonic current and the coupling relation of harmonic waves with different frequencies after passing through a converter can be described more accurately, and therefore the accuracy and reliability of an analysis result are improved, and a solid model foundation is provided for harmonic power flow research.

The invention relates to the technical field of power electronics and power transmission, and discloses a distributed multi-device differentiation and anti-interference cooperative harmonic suppression method, which comprises the steps of establishing a power generation data module, a power generation data analysis module, an execution module, an execution feedback module and an optimization upgrading module, the power generation data analysis module calculates data collected by the power generation data module and then establishes a harmonic impedance model in combination with the operation condition and historical data of the equipment, the execution module designs a specific harmonic suppression execution scheme of the harmonic impedance model, and the execution feedback module timely corrects the harmonic impedance model. And the model optimizing and upgrading module performs continuous optimizing and upgrading on the harmonic suppression method of the harmonic impedance model based on the power generation data accumulated for a long time, the feedback information of the execution feedback module and the actual operation experience of the execution module.

The invention discloses a distributed energy storage cluster access power distribution network harmonic resonance analysis method, which comprises the following steps of: aiming at system elements in a power distribution network, respectively constructing harmonic impedance models considering d-axis and q-axis asymmetric dynamic states under a dq coordinate system; injecting a small disturbance component, constructing a small disturbance modal impedance matrix Z of the whole system based on a harmonic impedance model, and obtaining a node voltage variation matrix according to the small disturbance component and the small disturbance modal impedance matrix Z; decomposing an inverse matrix of the small disturbance modal impedance matrix into a form of multiplying a left eigenvector matrix, a diagonal eigenmatrix and a right eigenvector matrix; and substituting the decomposed small disturbance modal impedance matrix into the node voltage variation matrix to obtain a linear relationship between a modal voltage vector and a diagonal eigenmatrix and a linear relationship between the modal voltage vector and a modal current vector, and obtaining a critical modal and a corresponding resonant frequency according to an eigenvalue of the diagonal eigenmatrix.

The invention discloses a harmonic stability evaluation method, device and equipment applied to a renewable energy power system and a medium, the method is applied to the technical field of power system harmonic, and the method comprises the steps: carrying out the impedance aggregation processing of topological structure data, and obtaining a harmonic impedance model; processing the renewable energy equipment data based on a Nyquist stability criterion to obtain a stability boundary condition of the power system; constructing a node admittance matrix based on the harmonic impedance model and the stability boundary condition; processing the node admittance matrix by using a Fourier technology to obtain impedance spectrum data, and processing the impedance spectrum data based on a modal impedance maximum value analysis method to obtain resonance modal characteristics; processing the resonance mode characteristics and the real-time operation condition to obtain a time domain verification result; and carrying out harmonic stability evaluation based on a time domain verification result. According to the method provided by the invention, the technical problem of harmonic stability evaluation distortion caused by incomplete measurement data can be solved.

The invention belongs to the technical field of power distribution network fault positioning, and provides a cable type power distribution network fault classification and positioning method, which comprises the steps of identifying a three-core cable structure and electrical parameters, constructing a normal and fault state model, generating a fault identification signal by using a power electronic switch combination of an additional power supply, and detecting a fault type. And obtaining short-circuit current data through phase-mode conversion, and calculating a fault distance by adopting a harmonic impedance method. According to the invention, the multi-frequency harmonic injection and power electronic switch combination technology is utilized to enhance the weak fault current detection capability; a phase-mode transformation method for expanding a Karenbauer matrix is adopted, and electromagnetic coupling interference between the guide core and the shielding layer is eliminated; a harmonic impedance fault distance measurement method reduces the distance measurement error; localized fault positioning is achieved through fast Fourier transform, and dependence on a remote monitoring system is reduced. According to the invention, high-precision, strong-disturbance-rejection and fast-response power distribution network fault positioning is realized, and an efficient technical scheme is provided for reliable operation of the intelligent power distribution network.

The invention provides a broadband high-efficiency filtering power amplifier and an output matching network design method thereof, and belongs to the technical field of wireless communication. The broadband high-efficiency filtering power amplifier comprises a power amplifier main body and an output matching network connected with the output end of the power amplifier main body; the output matching network structure is based on a three-mode transverse coupling filter; the output matching network comprises a plurality of transmission lines which are directly connected to form a first sub-network, a second sub-network, a third sub-network and a fourth sub-network; the structures of the first and second sub-networks are configured to be equivalent to a [lambda] / 4 transmission line having a harmonic impedance control function. Fundamental wave matching, harmonic control and filtering functions are integrated by adopting an output matching network structure: fundamental wave matching with a steep edge is realized by utilizing a three-mode transverse resonator, secondary harmonic impedance is controlled to a high-efficiency area by adopting an equivalent T-shaped lambda / 4 line, and while wide-bandwidth work is realized, the harmonic control and filtering functions are realized. And high efficiency and excellent harmonic suppression capability are realized.

The invention discloses a novel power grid harmonic compensation method and system based on harmonic responsibility division, and relates to the technical field of power grid harmonic compensation, and the method comprises the steps: collecting voltage and current signals at a common connection point of a power grid, and extracting each harmonic component from the voltage and current signals; based on each harmonic component, identifying harmonic impedance of a system side and a user side, and calculating a responsibility factor sequence corresponding to each harmonic; performing statistical analysis on the responsibility factor sequence in a preset time window to generate responsibility fluctuation entropy representing responsibility stability; dynamically correcting the compensation priority of each harmonic according to the responsibility factor and the responsibility fluctuation entropy corresponding to the responsibility factor; generating a harmonic compensation instruction of a non-user responsibility part according to the responsibility factor and the harmonic component after priority correction, and distributing available compensation capacity according to the priority when the capacity of a compensation device is limited; the method is applied to a system comprising a plurality of distributed power supplies with harmonic regulation and control capability.

The invention discloses a distributed photovoltaic power quality treatment method, system and device for multi-access point collaborative optimization and a storage medium, and relates to the field of distributed photovoltaic grid connection, and the method comprises the steps: carrying out the hierarchical division of a power distribution network, constructing a hierarchical collaborative management architecture, and implementing collaborative voltage support; photovoltaic output fluctuation and load demand data are combined to generate optimized topology and configure virtual impedance; in combination with the scene data, constructing and decomposing a multi-objective optimization model to obtain a reactive power distribution scheme; combining harmonic voltage and current data of each node to construct a harmonic impedance matrix to suppress harmonic waves; according to the invention, the voltage deviation can be controlled in a better range, and voltage shock is inhibited. The network loss is obviously reduced, and the economy is improved. The harmonic distortion rate is efficiently reduced, and interference is reduced. Parameters dynamically change along with scenes, the strategy switching success rate is improved, scene adaptability is enhanced, and powerful support is provided for safe, stable and economical operation of the power distribution network.

The invention discloses a method and a system for designing parameters of a cross-voltage-level active damping device for suppressing system resonance. The method comprises the following steps of: collecting resonance system parameters, determining a resonance frequency band range of a system according to a system impedance model, determining a resonance frequency and a corresponding initial harmonic voltage content ratio, and setting a target harmonic voltage content ratio; calculating harmonic current generated by the nonlinear load, and solving a damping value of system suppression resonance; determining the capacity of the active damping device according to the equivalent harmonic impedance, the harmonic current generated by the nonlinear load and the damping value of system suppression resonance, and carrying out cross-voltage grade transformer type selection; and designing a virtual resistance-capacitance value of the active damping device according to the parameters of the selected transformer and the damping value of the system for suppressing resonance. The insulation performance requirement of the active damping device is lowered, and the equipment treatment investment and the occupied area are reduced; and the influence of the cross-voltage level on the resistance-capacitance parameters of the device is fully considered, so that the parameter design result is more accurate, and the resonance suppression effect is further enhanced.

The invention discloses a filtering class F power amplifier based on a multimode resonator. The problems of large size and low efficiency caused by common design of a filter and an amplifier are mainly solved. The system comprises an input matching network, a grid electrode direct current feed network, a drain electrode direct current feed network, a transistor, a harmonic suppression network and a filtering matching network, and the input matching network utilizes a pi-shaped circuit to convert standard impedance of an input port into conjugation of optimal source impedance of the transistor; the grid and drain direct-current feed network isolates radio-frequency signals from entering a direct-current power supply and enables the transistor to work at a proper quiescent working point; the harmonic suppression network shapes the drain voltage and current of the transistor; the filtering matching network can control harmonic impedance and participate in matching, so that the drain electrode of the amplifier can reach the optimal load impedance. According to the invention, the loss generated by device connection is obviously reduced, the advantage of low complexity is shown, and the method is suitable for being applied to communication systems such as base stations and radars.

The invention discloses a multi-source dynamic power grid harmonic intelligent early warning method and system based on robust optimization, and relates to the technical field of electric power system monitoring, and the method comprises the following specific steps: data acquisition in a multi-source injection scene: through a distributed power supply monitoring device, a load monitoring device, a voltage transformer and a current transformer equipment, carrying out the multi-source injection scene; the output data of the distributed power supply and the real-time power data of the load are respectively collected, the change rule of the harmonic source can be accurately described by establishing the probability distribution models of the output and load change of the distributed power supply, and when the harmonic impedance of the power grid is dynamically monitored, the probability models are introduced and different actual operation conditions are simulated. The method comprehensively considers the influence of the uncertainty of the harmonic source on the harmonic impedance, obtains a harmonic impedance estimated value after the uncertainty factor is fully considered, achieves the dynamic and high-precision monitoring of the harmonic impedance of the power grid along with the change of time and working conditions, and provides a reliable basis for the accurate evaluation of the operation state of the power grid.

The invention relates to a micro-grid harmonic power distribution method and device, a control device and a readable storage medium. The method is applied to a control device of a micro-grid system. The control device is respectively connected with the inverters connected in parallel in the micro-grid system; the method comprises the steps of obtaining harmonic apparent power corresponding to each inverter according to a fundamental component of an output voltage of each inverter and each harmonic of an output current of each inverter; based on the harmonic apparent power, determining a harmonic power distribution coefficient corresponding to each inverter; obtaining harmonic compensation current required by each inverter according to the harmonic power distribution coefficient; and based on the harmonic compensation current and the harmonic power distribution coefficient, the equivalent harmonic impedance of the corresponding inverter is adjusted through the voltage and current double-closed-loop control loop corresponding to each inverter, so that the equivalent harmonic impedance is matched with the rated apparent power corresponding to the inverter. According to the invention, the harmonic current is reasonably distributed, and the voltage quality of the grid-connected point is ensured.

The invention discloses a box-type substation measurement and control system and method with a filter capacitor, and relates to the field of power monitoring. The objective of the invention is to solve the problems of poor filtering adaptability, single state monitoring dimension, high protection logic misjudgment rate, low service life prediction precision and low remote operation and maintenance efficiency in the prior art. The system comprises a self-adaptive filtering module, a multi-dimensional measurement and control module, an intelligent central control module, a hierarchical protection module, a dual-mode communication module and a local interaction module. According to the method, through multi-dimensional parameter acquisition, dynamic harmonic impedance matching and switching instruction generation, multi-sensor double-layer fusion diagnosis, multi-physics field aging prediction, three-level protection execution, data uploading and local interaction, organic fusion of dynamic harmonic treatment, multi-dimensional state perception, edge intelligent diagnosis and mechanism driving prediction is realized. The method is high in filtering adaptive capacity, comprehensive in monitoring, reliable in protection and efficient in operation and maintenance, the fault positioning precision reaches the branch level, conversion from passive response to active adaptation and early intervention can be achieved, and the method is suitable for a modern power distribution net box type transformer substation containing a distributed power supply.

The invention discloses a capacitor voltage transformer harmonic error prediction method based on NRBO-BP, and belongs to the technical field of modeling prediction. The method comprises the steps of analyzing harmonic transmission characteristics, adjusting stray capacitance numerical values to simulate different operating environments, performing simulation to obtain harmonic error data, optimizing initial weight and bias of a BP neural network by using an NRBO algorithm, constructing a harmonic error prediction model, and finally predicting 2-60 times of harmonic errors by taking typical harmonic errors as characteristic parameters. The performance of the model is evaluated by adopting a mean absolute error, a root-mean-square error and a decision coefficient, wherein the NRBO algorithm comprises the steps of population initialization, Newton-Raphson search and TAO trap avoidance; the method solves the problems of low model precision and susceptibility to environmental interference in the existing CVT harmonic error prediction, effectively improves the measurement precision of the CVT in the harmonic frequency band, and provides reliable technical support for harmonic analysis of a power system.

The utility model discloses a power amplifier, a transformer and a circuit module. The power amplifier comprises a differential cascode amplifier, a first neutralizing capacitor, a second neutralizing capacitor and a harmonic suppression unit. A common source electrode of the differential cascode amplifier is connected with a common grid electrode of the differential cascode amplifier to form a first node and a second node, and the first neutralizing capacitor and the second neutralizing capacitor are cross-coupled between a differential input end of the differential cascode amplifier and the first node and the second node. The harmonic suppression unit is connected among the first node, the second node and the ground voltage. According to the power amplifier, the transformer and the circuit module, by introducing the harmonic suppression unit, the fundamental frequency impedance and the second harmonic impedance of the power amplifier are adjusted, suppression of second harmonics is achieved, and the linearity of the power amplifier is improved. Meanwhile, the output impedance Q value of the amplifier is reduced, and compromise among linearity, efficiency and other performance indexes of an output matching network is optimized.

The invention relates to the technical field of embedded systems, in particular to an embedded system customized and developed for power application, which comprises a dynamic sensing module used for accurately capturing unsteady signals, the dynamic sensing module is coupled and connected with a real-time signal analysis module used for rapidly extracting features of the unsteady signals, and the real-time signal analysis module is coupled and connected with a data processing module. The real-time signal analysis module is in coupling connection with an intelligent scheduling module used for deterministic time delay of key tasks, and the intelligent scheduling module is in coupling connection with a fault-tolerant control module used for reliable operation under abnormal conditions. The method solves the problems that when an embedded system in the prior art adopts a fixed period FFT (128 points / 10ms), the amplitude capture delay of more than 13 times of harmonic waves reaches 15ms, so that the harmonic impedance calculation error exceeds 12%, and ADC sampling is possibly lost when a protection task and a data acquisition task conflict in priority, so that the sampling loss of the ADC is reduced. A power embedded system has the problems of missed detection of harmonic characteristics and conflict defects of task scheduling in a high dynamic load scene.

The invention relates to the technical field of intelligent power grid industry, and discloses a panoramic intelligent prediction system for harmonic impedance of a power system based on industrial big data. Comprising an electric power data acquisition module, an electric power data analysis module, an electric power fault pre-judgment module, an electric power fault response module, a user interaction interface module, a user feedback collection module and a prediction efficiency improvement module, the power fault pre-judgment module predicts system faults according to calculation results, the power fault response module performs targeted processing on the faults according to prediction results, and the user interaction interface module displays system operation states, fault prediction results and adjustment of system parameters to related workers by means of a visual interface. The user feedback collection module is responsible for collecting feedback information of a user in the system using process, and the prediction efficiency improvement module optimizes the whole system according to the user feedback information.

The invention discloses a harmonic interaction characteristic analysis method and device based on chaotic characteristics, equipment, a storage medium and a program product. The method comprises the following steps: obtaining harmonic impedance corresponding to a plurality of harmonic sources respectively; determining series impedance and parallel admittance of the power transmission line between the first harmonic source and the second harmonic source based on a pre-constructed equivalent circuit model of the power transmission line between the multiple harmonic sources, and determining equivalent connection impedance between the first harmonic source and the second harmonic source based on the series impedance and the parallel admittance; inputting the first harmonic impedance corresponding to the first harmonic source, the second harmonic impedance corresponding to the second harmonic source, the equivalent connection impedance and the Lyapunov exponent into a preset chaotic interaction factor calculation model to obtain a chaotic interaction factor between the first harmonic source and the second harmonic source; and determining an interaction characteristic analysis result between the first harmonic source and the second harmonic source based on the chaos interaction factor. Therefore, the stability of the multi-harmonic source system is improved.

The embodiment of the application provides a power amplifier circuit, a radio frequency front end module and a communication device, relates to the technical field of electronics, and is used for improving the saturation power and saturation efficiency of the power amplifier circuit. The power amplifier circuit adopts an impedance matching network architecture of series connection of a capacitor and an inductor in at least one branch (which can be a main power amplifier branch or a peak power amplifier branch). Under the architecture, the fundamental wave impedance and the harmonic impedance of the branch are both adjusted by the series connection capacitor and inductor network. However, since the capacitance of the capacitor and / or the inductance of the inductor can be changed, the fundamental wave impedance is fixed, and the second harmonic impedance is changed. That is, when the second harmonic impedance is adjusted in a wideband range, the fundamental wave impedance can not be affected. Based on this, by reasonably selecting the capacitance of the capacitor or the inductance of the inductor, the fundamental wave impedance and the second harmonic impedance in the branch can meet the requirements respectively, so that the power amplifier circuit has relatively optimal saturation power and saturation efficiency.

The application discloses an active power filter control method for preventing resonance, and relates to the technical field of power quality control.The method injects a harmonic current with a frequency of a pre-judged harmonic frequency into a power supply circuit, compares the change in the grid-side current and the load-side current before and after the injection, obtains a sensitive frequency point, separates the harmonic component corresponding to the sensitive frequency point from the harmonic components corresponding to other frequencies, and respectively generates compensation currents, wherein the harmonic component corresponding to the sensitive frequency point is adjusted through a feedback coefficient, different compensation currents are superimposed to obtain a comprehensive compensation current, the comprehensive compensation current is used to offset the load harmonic current, and the grid-side current is ensured to be undistorted.The technical scheme in the application can realize harmonic impedance adjustment, effectively prevent harmonic amplification, avoid passive element burning or power supply failure, and enhance the safety and reliability of power supply.

This invention discloses a power system equivalent harmonic impedance identification strategy based on physical consistency constraints, comprising the following steps: First, voltage and current data at the common coupling point in the power system are collected, frequency domain analysis is performed on the data to obtain harmonic components, and the harmonic components are normalized and feature-processed to form a feature dataset for model training; then, a multilayer feedforward neural network (MLP) data-driven module and a physical information neural network (PINN) physical constraint module are designed, and a self-attention temporal convolution feature module is fused to construct a multilayer feedforward-attention physical information neural network (MLP-APINN) model; finally, the model is trained using a first-order gradient parameter iteration method, and the model parameters are updated using a learning rate adjustment strategy to obtain the identification result of the system-side equivalent harmonic impedance; this invention improves the stability and generalization performance of harmonic impedance identification by introducing physical consistency constraints, and is applicable to harmonic impedance identification at the common coupling point in the power system.

A kit for monitoring an oil-immersed or oil-filled transformer 4 comprises: a communication device 1 and at least three sensors 3 to determine different characteristics of the transformer. The sensors are connected to the communication device using cables and the communication device forwards measured sensor data to a remote database 5. The sensors may measure temperature, humidity, gas content, partial discharge, pressure, liquid level, power, frequency, phase angle, harmonics, impedance, insulation or grounding resistance, earth fault current, arcs, overload or short circuit. Top oil temperature, bottom oil temperature, ambient temperature and winding current may particularly be measured. The kit may be installed to upgrade or service an existing transformer. The measured data may be encrypted before transmission or a certificate may be used to authorize communication. The kits may be used to monitor a fleet of installed transformers remotely.

The invention relates to the technical field of power system protection, and discloses a direct-current line bipolar short-circuit fault protection method based on harmonic impedance, which comprises the following steps: measuring a voltage waveform signal and a current waveform signal of a direct-current line protection position in real time; processing the voltage waveform signal and the current waveform signal by adopting short-time Fourier transform, and extracting a high-frequency voltage component and a high-frequency current component of a specific harmonic order; calculating a module value and a phase angle of the high-frequency voltage component and a module value and a phase angle of the high-frequency current component, and obtaining harmonic impedance through voltage division calculation; the fault position is determined according to the harmonic impedance change of each line before and after the fault occurs; the fault position is determined through the harmonic impedance change of each line before and after the fault occurs, and a rapid, reliable and economical protection scheme is provided for the bipolar short-circuit fault of the direct-current line.

The invention provides a power distribution network harmonic instability critical damping dynamic early warning method and system. The method comprises the steps that harmonic voltage and harmonic current of key nodes of a target power distribution network are acquired every first preset time; identifying the harmonic voltage and the harmonic current according to a first preset rule so as to obtain equivalent harmonic impedance under a preset harmonic frequency according to an identification result; calculating a system damping ratio corresponding to a preset harmonic frequency according to the equivalent harmonic impedance; judging whether the system damping ratio is smaller than or equal to a preset damping ratio threshold value; and if the system damping ratio is smaller than or equal to the preset damping ratio threshold value, generating a harmonic instability early warning signal. According to the invention, the accuracy and practicability of early warning can be effectively improved.

The application provides an online identification method for harmonic resonance of a power system, comprising the following steps: collecting voltage waveform data and current waveform data at a preset common coupling point in the power system, pre-processing to obtain waveform difference degree, performing multiple transformations on the collected voltage waveform data and current waveform data to obtain current complex matrix and voltage complex matrix of a fundamental wave and each harmonic; determining a fundamental wave and a total harmonic impedance amplitude array of the common coupling point according to an equivalent model of the power system; calculating power factors of the fundamental wave and each harmonic, and obtaining a power factor array after screening; and determining that harmonic resonance occurs in the power system when the waveform difference degree, the harmonic number array and the power factor array simultaneously satisfy a preset resonance condition. The application combines the similarity of the collected waveforms, harmonic impedance and power factors of multiple parameters, and only needs voltage and current waveform data at the PCC point to identify the harmonic resonance in the power system.

The present invention discloses a load modulation power amplifier and a corresponding electronic device. The load modulation power amplifier includes a driver stage power amplifier and its bias circuit, an input power divider, a harmonic impedance controller, a main path power amplifier and its bias circuit, a secondary path power amplifier and its bias circuit, and a load modulation combiner. Among them, the driver stage power amplifier is provided with a bias circuit with enhanced transconductance, the main path power amplifier is provided with a bias circuit with adjustable phase, and the secondary path power amplifier is provided with a bias circuit with controllable turn-on power point. Cooperating with a harmonic impedance matching circuit and a load modulation combiner with low insertion loss, each unit works together to achieve the linearization and high efficiency of the load modulation power amplifier, which can well meet the requirements of practical applications.