471 results about "Harmonic voltages" patented technology

The invention relates to an intelligent power distribution harmonic monitoring and dynamic compensation system which comprises a monitoring unit, a correction unit and a compensation unit. The monitoring unit continuously collects high-frequency harmonic voltage and current data in a distribution line at a high sampling frequency, extracts transient harmonic components through wavelet packet transformation and empirical mode decomposition, and generates low-dimensional feature vectors based on sparse representation. And the correction unit decodes the low-dimensional feature vector, recovers harmonic time-frequency features, calculates a phase drift rate, predicts a harmonic propagation path and an accumulation node by combining real-time power distribution network topology construction and adopting a nonlinear dynamic prediction model, and generates a correction instruction when abnormality is detected. And the compensation unit adopts pulse sequence density modulation to dynamically adjust a compensation current phase according to the correction instruction, and meanwhile, an inductive coupling device is utilized to transfer harmonic energy to a low-risk node, so that harmonic voltage distortion of a target node is quickly recovered to a stable level in a fundamental wave period after early warning.

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 discloses a new energy station harmonic emission level evaluation method and system based on recording data, and the method comprises the steps: carrying out the wavelet threshold de-noising processing of the recording data of line current and bus voltage in a power grid, and then carrying out the Fourier analysis, and obtaining the amplitude and phase angle of each harmonic current and voltage; on the basis of the amplitude and phase angle of each harmonic current and voltage, the harmonic order to be analyzed is determined through the harmonic voltage content rate and the harmonic distortion rate, an abnormal bus is screened as a concerned bus, and suspicious harmonic source users in the power grid are identified; establishing an equivalent model of the power grid, and solving harmonic transfer impedance between each suspicious harmonic source user and the concerned bus in the equivalent model by using a blind source separation algorithm; and quantifying the harmonic responsibility of each suspicious harmonic source user to the concerned bus. According to the invention, the accuracy of harmonic evaluation and the accuracy of tracing are improved, and the improvement of the electric energy quality of a new energy station and the stable operation of a power grid are facilitated.

The invention discloses an island detection method based on harmonic dynamic characteristics and reactive slip collaborative identification and a detection system thereof, and relates to the field of new energy island detection. In order to solve the defects of low feature extraction precision, threshold stiffness and insufficient response speed of existing island detection, an operation data set of a micro-grid system is acquired according to a topological structure of the micro-grid system; dynamic characteristic data fusion processing is implemented, and harmonic voltage is calculated; a harmonic voltage break variable is used as a starting criterion of island detection; sequentially judging whether the harmonic voltage break variable, the fundamental voltage amplitude and the offset of each harmonic voltage are out of limit or not so as to judge whether the micro-grid is in an island state or not; and constructing a virtual orthogonal signal to calculate a three-phase reactive slip ratio, judging whether the three-phase reactive slip ratio is out of limit, if not, determining that the microgrid is in a non-islanding state, and if yes, determining that the microgrid is in an islanding state. The method is mainly used for judging whether the microgrid is in the island state or not.

The invention relates to the technical field of cable line power distribution network harmonic resonance treatment, in particular to a global and local cooperative partition cooperative resonance suppression method and device. The method comprises the steps of determining a harmonic conductance sensitivity index of each node in a power distribution network according to a target power distribution network admittance matrix parameter, and performing node region division; performing modal analysis on the admittance matrix parameters to obtain modal impedance and participation factors; determining a global optimal virtual admittance instruction value according to the modal impedance, the participation factor and the voltage distortion rate; according to the global optimal virtual admittance instruction value and the voltage distortion rate, determining a regional optimal virtual admittance instruction value in the region; and determining a harmonic compensation current value according to the regional optimal virtual admittance instruction value and the harmonic voltage. According to the method, harmonic suppression is realized for the whole power distribution network by adopting a partition and cooperation mode, and meanwhile, for background harmonic injection change, external interference such as resonance center offset and the like can be effectively overcome, so that the optimal harmonic suppression effect is realized.

The invention discloses a power supply reliability analysis method and system based on operation and maintenance characteristics of a power distribution network, and particularly relates to the technical field of power supply analysis of the power distribution network. Harmonic data, including harmonic current, harmonic voltage and frequency components, of each node in a power distribution network system are collected in real time; in combination with the topological structure of the power distribution network, the sparse linear equation set is solved through L1 norm optimization, and the main source of harmonic waves is identified; the contribution degree of each nonlinear load to the harmonic distortion of a power distribution network system is calculated, a list of key harmonic sources is screened out through Pareto analysis, a filter configuration optimization model is constructed based on the identified key harmonic sources, and the harmonic distortion level and the filter installation cost are used as constraint functions to optimize the filter configuration. The installation position and the parameter configuration of the filter serve as decision variables, an optimization algorithm is adopted for solving, and the recommended installation position and the parameter configuration of the filter are output; the harmonic suppression effects under different load conditions are evaluated, and the problem that the power supply reliability is reduced due to harmonic distortion is effectively solved.

The invention discloses a distributed photovoltaic power quality monitoring method. The method comprises the following steps: acquiring original waveform data of the Internet of Things in real time through a serial peripheral interface; calculating cyclic wave voltage amplitude, cyclic wave harmonic voltage and / or current amplitude, inter-harmonic voltage and / or current amplitude, harmonic active power, positive sequence, negative sequence and zero sequence components of voltage and / or current and unbalance degree according to the original waveform data; and calculating an instantaneous flicker value through a filter according to the original waveform data, and carrying out transient rise, transient drop and interruption event monitoring according to the original waveform data. According to the invention, the technical problems of how to monitor the electric energy quality quickly in real time and how to calculate the frequency deviation in real time are solved.

The invention discloses a current coordinated distribution and voltage optimization control method of a multi-network converter considering nonlinearity and negative sequence load. The method comprises the following steps: carrying out harmonic separation on three-phase load side current and three-phase capacitor voltage through feedforward compensation to obtain a fundamental wave positive sequence component, a fundamental wave negative sequence component and an h-order harmonic component; fundamental wave positive sequence active and reactive power are solved, and angular frequency and output voltage are respectively obtained through an active frequency regulator and a reactive voltage regulator; virtual impedance of a fundamental wave positive sequence, a fundamental wave negative sequence and a harmonic component is set, a multi-frequency-point virtual impedance voltage drop instruction is calculated, and a voltage reference instruction value is obtained by subtracting the multi-frequency-point virtual impedance voltage drop instruction value from the output voltage of the constructed network type converter; calculating a three-phase modulation wave signal based on the voltage reference instruction value, the capacitor voltage, the load side current, the inductor current and the DC voltage; and calculating a pulse signal of the switching device based on the three-phase modulated wave signal. The virtual impedance of the networking converter is set to be a negative value, the harmonic voltage drop on a common coupling point can be reduced, the sum of the virtual impedance and the actual impedance is adjusted to be a certain proportion, and the harmonic current of each order of the multi-networking converter can be distributed according to the proportion.

The invention discloses a new energy power grid probability harmonic load flow calculation method based on improved semi-invariant and Gram-Charlier series expansion. The new energy power grid probability harmonic load flow calculation method comprises the following steps: establishing a random variable probability model, a wind-light output model and a wind-light joint distribution model; secondly, considering the output correlation between wind and light fields, converting the wind and light combined distribution model based on a Copula function into independent variables by utilizing Rosenblatt conversion for calculation, then calculating each-order semi-invariant of load, photovoltaic output and wind power output according to the expected values of node voltage and branch power flow and a sensitivity matrix, and finally calculating the output correlation between the wind and light fields according to each order semi-invariant of the load, the photovoltaic output and the wind power output. The method comprises the following steps of: obtaining a state variable, further solving each-order semi-invariant form of the state variable and the branch power flow, and finally, obtaining a probability density function and a probability distribution function of harmonic voltage of each node by combining Gram-Charlier series expansion.

The invention relates to the field of power distribution network bearing capacity analysis, in particular to a multi-dimension-based power distribution network photovoltaic bearing capacity evaluation method and system, and aims to solve the problems that HC evaluation is inaccurate and the real-time requirement is difficult to meet in the prior art. According to the method, firstly, a multi-dimensional voltage quality index measurement space including voltage deviation, voltage unbalance degree and voltage fluctuation amplitude is constructed, and a comprehensive operation constraint model is established in combination with a total harmonic voltage distortion rate and an individual harmonic voltage distortion rate; thirdly, learning a complex nonlinear time sequence mapping relation between a time sequence of a power grid multi-dimensional state in historical operation data and the maximum allowable photovoltaic bearing capacity meeting the strict constraint conditions by using a BILSTM network; by comprehensively considering the key power quality and the harmonic constraint and applying the strong time sequence information processing capability of the BILSTM, the accuracy and robustness of HC evaluation are remarkably improved.

The invention discloses a SiC MMC sub-module capacitor voltage fluctuation suppression method and system, and belongs to the technical field of electronic power. According to the analysis result of the optimal broadband harmonic circulation injection boundary and number of times of the SiC MMC sub-module, a sub-module capacitor voltage fluctuation optimization model for simultaneously injecting second, fourth and eighth harmonic circulation and third harmonic voltage is determined, and the characteristic of higher control bandwidth of the SiC MMC can be fully utilized; by solving a submodule capacitor voltage fluctuation optimization model, the amplitudes and phases of reference values of second, fourth and eighth harmonic circulation needing to be injected and the amplitude and phase of corresponding third harmonic voltage are determined, then the second, fourth and eighth harmonic circulation is injected, and the third harmonic voltage injection is combined to realize broadband harmonic combined injection. The capacitance voltage fluctuation of the sub-module is reduced, the capacitance voltage fluctuation suppression method for the SiC MMC sub-module is realized, and the suppression effect is relatively high.

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.

This invention discloses a method and system for suppressing capacitor voltage fluctuations in SiC MMC submodules, belonging to the field of electronic power technology. Based on the analysis results of the optimal broadband harmonic circulating current injection boundary and order for SiC MMC submodules, an optimized model for submodule capacitor voltage fluctuations is determined that simultaneously injects 2nd, 4th, and 8th harmonic circulating currents and 3rd harmonic voltages, which can fully utilize the higher control bandwidth characteristic of SiC MMC. By solving the optimized model for submodule capacitor voltage fluctuations, the amplitude and phase of the reference values ​​of the 2nd, 4th, and 8th harmonic circulating currents to be injected, as well as the amplitude and phase of the corresponding 3rd harmonic voltage, are determined. Then, by injecting 2nd, 4th, and 8th harmonic circulating currents and jointly injecting the 3rd harmonic voltage, broadband harmonic joint injection is achieved, reducing the capacitor voltage fluctuations of the submodule and realizing a method for suppressing capacitor voltage fluctuations in SiC MMC submodules with high suppression effect.

The invention relates to a fusion power supply harmonic suppression method based on an energy storage type STATCOM. The method comprises the following steps: determining a harmonic amplification factor K value; selecting and designing a proper discrete digital band-pass filter, and detecting a target frequency band and filtering characteristic sub-harmonics; the detected harmonic voltage amplitude and phase are used as references, an energy storage type STATCOM is adopted to output same-frequency and same-phase harmonic current, virtual damping is formed at a grid-connected point, a K value is used as a damping coefficient, the output harmonic current reference amplitude is determined, virtual harmonic damping is controlled, and harmonic resonance is suppressed. The virtual harmonic damping method for the energy storage type STATCOM is provided for accurate tracking of low-frequency harmonic and inter-harmonic voltage amplitudes and phases, the chain type STATCOM has the advantages of being high in high-voltage direct-hanging efficiency, high in redundancy fault-tolerant capability and the like and is suitable for high-voltage large-capacity scenes, virtual damping control achieves harmonic suppression by adjusting virtual damping at the harmonic frequency of a control structure, and the energy storage type STATCOM can be applied to high-voltage large-capacity scenes. And the system stability can be effectively improved while harmonic waves are treated.

The invention discloses a model prediction control method of a high-speed permanent magnet synchronous motor and a related device, and relates to the field of control, and the method comprises the steps: building a stator current equation capable of simulating the behavior of the high-speed permanent magnet synchronous motor based on the position change of a rotor in the same control period, a high control input basic voltage value is obtained by fixing motor parameters and combining a total disturbance parameter of a current loop system and a set stator current tracking target at the next moment at the same time; on the basis of the control input basic voltage value, current loop harmonic voltage compensation is carried out through the control input harmonic compensation voltage value to obtain a control input voltage value, and voltage modulation is carried out according to the control input voltage value to control the high-speed permanent magnet synchronous motor. According to the method, when the stator current equation is constructed, rotor position change parameters in the same control period are innovatively introduced, so that the motor behavior simulation precision is remarkably improved; the defect that the switching frequency is not fixed in a traditional finite set model predictive control algorithm is effectively overcome through the voltage modulation technology.

The invention belongs to the technical field of power electronics, and provides a method and a system for improving harmonic transient stability of a grid-forming type active power filter, droop control is performed on a deviation value of an active power reference instruction and an actually measured active power value, integration is performed to obtain a power angle, and the power angle and a grid-side harmonic phase are added to generate a harmonic voltage phase instruction; pI control is carried out on a deviation value between the reactive power reference instruction and an actually measured reactive power value to obtain a voltage deviation value, and the voltage deviation value and a network side specified subharmonic voltage amplitude are summed to generate a harmonic voltage amplitude instruction; taking a harmonic voltage amplitude instruction as a d-axis reference, taking 0 as a q-axis reference, respectively subtracting the d-axis reference and the q-axis reference from the harmonic voltage on the d-axis and the q-axis to obtain deviation values, and obtaining a dq component of the harmonic voltage reference through PI control. The operation safety of the power grid can be improved.

The invention discloses a ground fault positioning and multi-solution screening method for a stator winding of a pumped storage unit, and belongs to the field of relay protection. The method is combined with a special structure of a stator winding of a variable-speed pumped storage unit, and a function relationship between a fault winding potential and a fault position is established by taking a slot potential as an analysis unit. In a phasor plane, by drawing a three-phase ground voltage phasor and a neutral point voltage phasor, an included angle relation between a fault point voltage phasor and the neutral point voltage phasor and a phasor triangle relation are utilized to determine an alternative fault point. And then, an optimization model for fault positioning is established, and a homonuclear molecule optimization algorithm is adopted for solving, so that accurate positioning of a plurality of alternative fault points is realized. And finally, third harmonic voltage information is introduced as auxiliary information, and a unique solution is screened out from the plurality of alternative fault points. The method is high in reliability, small in positioning result error and suitable for the positioning requirement of the variable-speed pumped storage unit stator grounding fault.

The invention provides a voltage and current harmonic coordinated suppression method and system based on a power electronic converter, the method works in a typical scene of distributed power supply network construction and network-following hybrid control, and the method comprises the following steps: using extracted load current harmonic as a network-following converter harmonic control instruction to suppress load harmonic current; a harmonic virtual impedance method is adopted to adjust the grid-connected harmonic voltage of the grid-forming converter, so that the harmonic content of voltage and current is inhibited in a coordinated manner. According to the method, the equivalent power supply characteristics of network construction and network following are fully utilized, comprehensive treatment of the background harmonic voltage and harmonic current of the power grid is realized, and the network access electric energy quality of the grid-connected system under the weak network is improved.

The invention discloses a specific grid-connected current harmonic suppression method and device for an energy storage converter, and belongs to the technical field of power systems, and the method comprises the steps: obtaining a given current value of a fundamental current loop, and carrying out the dq / abc conversion to obtain a three-phase current reference value; acquiring a three-phase current value of a power grid side, and subtracting the three-phase current value from the three-phase current reference value to obtain a harmonic current value; converting the harmonic current value to a target subharmonic synchronous rotating coordinate system to obtain a target subharmonic current value; extracting the target sub-harmonic current value in a direct current form through a low-pass filter, and sending the target sub-harmonic current value to a PI regulator for regulation to obtain a harmonic voltage compensation amount; and injecting the harmonic voltage compensation amount into a modulation wave to realize suppression of the target subharmonic current. According to the invention, the grid-connected side current harmonic of the energy storage converter can be effectively suppressed, and the grid-side current quality is improved.

The invention discloses a torque ripple suppression method and control device based on permanent magnet flux linkage harmonic identification, and the method comprises an online identification process and a torque ripple suppression process, and is used for suppressing the torque ripple of a built-in permanent magnet synchronous motor. The online identification process comprises a permanent magnet flux linkage harmonic identification step, a dead zone voltage harmonic compensation step and a harmonic component extraction step; the torque ripple suppression process comprises the steps of inputting a pre-recognized flux linkage harmonic lookup table to obtain fifth and seventh permanent magnet flux linkage harmonics, predicting torque ripple according to a magnetic co-energy model, outputting an optimal stator current reference value, obtaining sixth harmonic voltage for suppressing the torque ripple, and driving the motor by using an SVPWM strategy after a fundamental component and a harmonic component are superposed.

The invention discloses a harmonic suppression method and device, a permanent magnet synchronous motor and a storage medium, and relates to the technical field of motor control, and the harmonic suppression method is applied to the permanent magnet synchronous motor, and comprises the steps: carrying out the harmonic extraction of a stator current of the permanent magnet synchronous motor, and obtaining a fifth harmonic current component of the stator current; determining the quintuple harmonic voltage compensation amount of the stator current according to the quintuple harmonic current component of the stator current; and performing voltage feed-forward compensation on the permanent magnet synchronous motor based on the quintuple harmonic voltage compensation amount of the stator current. On the basis of ensuring that the influence of the higher harmonic current generated in the operation process of the permanent magnet synchronous motor on the rotating speed and the torque of the motor is controlled within an acceptable range, the engineering realization difficulty is effectively reduced.

The invention discloses an electric power system harmonic propagation analysis method and device and a storage medium, and belongs to the technical field of electric power system harmonic analysis, and the method comprises the steps: inputting a to-be-predicted operation condition parameter and a harmonic voltage parameter into a trained regression prediction model, obtaining a corresponding prediction cross admittance matrix, and obtaining a prediction cross admittance matrix; the predicted cross admittance matrix is applied to harmonic propagation analysis of the power system; wherein the regression prediction model is integrated with Bagging based on a decision tree; according to the method, by improving the data set quality and optimizing the model hyper-parameters, the harmonic source cross admittance matrix which is self-adaptive to the operation condition and is established by adopting the decision tree-based regression device and the Bagging element regression device can meet the harmonic analysis precision requirements under different operation conditions, and harmonic propagation of the power system can be analyzed more accurately; the analysis efficiency is improved, and a feasible technical path is provided for online monitoring or rapid evaluation.

The invention discloses a harmonic current calculation method and device, equipment and a storage medium. The method comprises the following steps: acquiring power grid parameters after a photovoltaic inverter is connected to a power grid; performing rotation transformation on the power grid parameters to obtain a voltage harmonic phasor under a rotating coordinate system; an equivalent control circuit of the photovoltaic inverter is constructed, a current dq-axis component matrix of a PCC node is obtained based on the equivalent control circuit, and the PCC node is a coupling common point of the photovoltaic inverter and a power grid; the current dq-axis component matrix of the PCC node is converted into a current harmonic phasor matrix with a voltage harmonic phasor as an excitation condition; and performing decomposition calculation on the current harmonic phasor matrix to obtain harmonic current. And calculating the harmonic voltage to obtain a harmonic current, so as to evaluate the operation possibility of the photovoltaic inverter under the distorted power grid under different conditions through the harmonic current.

The invention discloses an offshore wind power harmonic traceability method and system based on Bayesian regression, and the method comprises the steps: calculating a voltage fluctuation value and a current fluctuation value of each time node through obtaining harmonic voltage time sequence data and harmonic current time sequence data of a to-be-evaluated node; a harmonic impedance estimation mathematical model is constructed according to a voltage fluctuation value and a current fluctuation value; the harmonic impedance estimation mathematical model is solved based on the Bayesian theorem, system side harmonic impedance parameters are obtained, fluctuation of system side harmonic impedance is accurately tracked, and user side harmonic responsibility and system side harmonic responsibility are quantified according to the system side harmonic impedance parameters, harmonic voltage time sequence data and harmonic current time sequence data; and finally, determining the position of a harmonic source according to the user side harmonic responsibility and the system side harmonic responsibility, and accurately realizing harmonic traceability when the impedance changes.

The invention discloses a harmonic suppression method and system based on feedforward control and virtual impedance, and belongs to the field of electric energy quality control, and the method comprises the steps: constructing a harmonic extraction model based on the cascading of double third-order generalized integrators, and obtaining a voltage harmonic component based on the harmonic extraction model and real-time power grid data; based on a preset power outer loop control strategy, a preset voltage and current double closed loop control strategy, a preset harmonic voltage feed-forward control strategy and the voltage harmonic component, constructing a network construction type charging pile control model, and obtaining an initial output current; obtaining each virtual impedance based on the initial output current, the harmonic extraction model and the voltage harmonic component; and obtaining a harmonic suppression model based on each virtual impedance and the network construction type charging pile control model, so as to obtain a harmonic suppression output current based on the harmonic suppression model and the real-time power grid data. According to the harmonic suppression method and system based on feedforward control and virtual impedance provided by the invention, grid-connected output current harmonics controlled by a network-forming type charging pile are effectively suppressed.

The invention discloses a resonance identification method and system based on cross-voltage-level harmonic monitoring data. The method comprises the following steps: synchronously sampling cross-voltage-level monitoring amplitude data of a high-voltage side and a low-voltage side of a main transformer; calculating a first correlation coefficient of concerned frequency harmonic voltage and harmonic current of the low-voltage side of the main transformer, and judging whether the power grid generates resonance or not based on the first correlation coefficient; when resonance occurs, according to the cross-voltage level monitoring amplitude data, calculating the concerned frequency harmonic voltage content ratios of the high and low voltage sides; calculating a harmonic voltage transfer coefficient according to the concerned frequency harmonic voltage content ratios of the high and low voltage sides; calculating a second correlation coefficient between the harmonic voltage transfer coefficient and the load rate of the main transformer, and identifying the position of the resonance source based on the second correlation coefficient; identifying the resonance type based on the harmonic voltage transfer coefficient when the resonance source is located at the power grid side; the resonance type is identified based on a third correlation coefficient between the low-voltage-side frequency-of-interest harmonic voltage content and the main transformer load rate when the resonance source is located on the load side.

The invention belongs to the technical field of power quality of a power distribution network, and discloses a dominant harmonic source identification method and system.The dominant harmonic source identification method comprises the steps that on the basis of power grid phase-free measurement data collected in real time, the nonlinearity of each feeder line in a power grid is judged through nonlinear analysis, and the feeder lines containing harmonic sources are screened; according to the screened feeder lines containing the harmonic sources, utilizing a correlation analysis algorithm to solve a correlation index between the harmonic voltage of the common connection point and the harmonic current of each feeder line, and calculating a nonlinearity index of each feeder line containing the harmonic sources; and performing weighted summation on the correlation indexes and the nonlinearity indexes by using an objective weighting method to obtain fusion indexes of the feeder lines, and identifying the dominant harmonic source according to the size of the fusion index of each feeder line. According to the method, harmonic wave responsibility division can be efficiently and accurately realized, the identification result is not interfered by background harmonic wave fluctuation, and the method has good stability.

The invention provides a harmonic source modeling method based on time-frequency feature extraction. The method comprises the following steps: firstly, determining harmonic principal component frequency of a harmonic source; extracting harmonic voltage amplitude and phase angle corresponding to harmonic principal component frequency of the harmonic source to obtain a harmonic source frequency domain feature set; reconstructing the frequency domain feature set through IDFT to form a harmonic source frequency domain feature component matrix, and splicing the harmonic source frequency domain feature component matrix with an original voltage sequence acquired by a synchronous phasor measurement device to obtain a time-frequency feature component matrix; converting the component matrix into a grey-scale map by using a matrix normalization method, and converting the grey-scale map into a three-channel time-frequency characteristic component color map by using a pseudo-color coding technology; and finally, taking the acquired harmonic source voltage data and the time-frequency characteristic component color map as the input of the model, taking the acquired corresponding harmonic source current data as the output of the model, and continuously training the network model through the actually measured data until the accurate mapping of the relation between the harmonic voltage and the harmonic current of the harmonic source is realized. And obtaining a harmonic source data driving model.

The invention discloses a harmonic analysis method, system and device for a flexible direct current converter and a medium, and relates to the technical field of flexible direct current transmission, and the method comprises the steps: obtaining key electrical parameters of a to-be-tested flexible direct current converter; constructing a high-frequency equivalent circuit corresponding to each target device according to the key electrical parameters; calculating a harmonic voltage component of a single bridge arm of a converter valve in the to-be-tested flexible DC converter according to the key electrical parameters so as to generate a harmonic voltage source; integrating the high-frequency equivalent circuit and the harmonic voltage source into simulation software for transient simulation; and determining harmonic voltage distribution and harmonic current distribution of the to-be-tested flexible direct current converter according to the simulation result, thereby effectively avoiding the equipment operation risk and reducing the fault rate of the flexible power transmission equipment.

A multivariable optimization design method for improving counter electromotive force of a permanent magnet motor for a flywheel comprises the steps that firstly, after the size structure of the motor is determined, electromagnetic modeling of the motor is completed, and optimization variable parameters and a counter electromotive force optimization target of the motor are defined; calculating the sensitivity of different optimization variable parameters by using a sensitivity hierarchical calculation method; high-sensitivity parameters are selected for further optimization design, and a response surface equation between the optimization variable parameters and the back electromotive force optimization target is sampled, calculated and optimized; and a genetic algorithm is used to solve the optimal design solution of the back electromotive force performance, and when the amplitude of the back electromotive force fundamental wave is maximum and the amplitudes of the third and fifth harmonic voltages are minimum, the back electromotive force performance is the best. The permanent magnet motor for the flywheel is easy to process and high in pertinence, the electric energy quality of the permanent magnet motor for the flywheel can be obviously improved, and the problems of small counter electromotive force and poor electric energy quality in the permanent magnet motor for the flywheel are solved.