38 results about "Harmonic model" patented technology

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 signal processing, in particular to a periodic signal modeling method and device, electronic equipment and a storage medium, and the method comprises the steps: obtaining a coordinate time sequence of a target navigation satellite system; preprocessing the coordinate time sequence to obtain a preprocessed coordinate time sequence, and correcting the preprocessed coordinate time sequence to obtain a corrected coordinate time sequence; estimating the corrected coordinate time sequence to obtain a sine coefficient of periodic amplitude, a cosine coefficient of periodic amplitude and periodic frequency deviation; the method comprises the following steps: establishing a coordinate time sequence model, decomposing, establishing an initial harmonic model, estimating to-be-estimated parameters of the initial harmonic model by using a preset estimation strategy to obtain an estimation result, and establishing a final harmonic model according to the estimation result and the initial harmonic model, thereby solving the problem of systematic deviation caused by empirical period length assumption in coordinate time sequence modeling. And the seasonal deformation inversion precision and the earth crust movement rate estimation reliability are improved.

The invention relates to the field of voice signal processing and voice recognition, and discloses a voice recognition enhancement method and system based on harmonic model fundamental frequency optimization and RNN noise suppression, and the method comprises the steps: collecting a voice signal in a noise environment in real time, carrying out the framing and windowing of the voice signal, and generating multi-dimensional time-frequency data; estimating the fundamental frequency of each frame of voice through a cepstrum analysis method, and screening effective fundamental frequency frames according to a confidence coefficient threshold to form a fundamental frequency characteristic matrix; dynamically adjusting the noise power spectrum of the Wiener filter under the drive of the fundamental frequency characteristic matrix, and carrying out dislocation fusion on the filtering output and the original spectrum to form an enhanced spectrum first draft; inputting the enhanced spectrum first draft into a recurrent neural network in a framing manner, predicting the gain of each frequency band, calculating an inhibition factor, and generating a multi-frame continuous enhanced spectrum sequence; multiple frames of continuous enhanced spectrum sequences are synthesized into voice signals through inverse short-time Fourier transform, an end-to-end enhanced recognition process is formed, and the method has the advantage of improving accuracy.

The invention discloses a dual three-phase permanent magnet synchronous motor harmonic suppression method based on virtual back electromotive force identification, and the method comprises the following steps: S1, building a driving system model of a DTP-PMSM; s2, constructing a harmonic model of the DTP-PMSM, analytically decomposing the nonlinear characteristic and the non-sinusoidal counter electromotive force of the inverter into dq and dqz subspaces, introducing the concept of virtual harmonic counter electromotive force, and unifying the nonlinearity of the inverter, the space harmonic counter electromotive force and cross coupling terms related to harmonic current into a single expression form; and S3, developing an identification principle based on current mapping, including amplitude and phase estimation, gain design and delay compensation, so as to estimate the amplitude and phase deviation of the virtual harmonic back electromotive force on line to realize harmonic suppression and avoid a complex algorithm and a large amount of parameter adjustment. According to the method, the operation effect is good in a wide rotating speed range, and meanwhile complex algorithms and a large amount of parameter adjustment are avoided.

The invention discloses a large power grid harmonic calculation method and system considering conventional direct current and flexible direct current, and belongs to the technical field of power system harmonic simulation. The method comprises the following steps: acquiring power grid operation mode data of a power grid, and constructing harmonic models of various elements of the power grid based on the power grid operation mode data; judging whether the current power grid operation mode comprises conventional direct current and flexible direct current or not, if so, acquiring operation data of the conventional direct current and the flexible direct current from the operation mode, and calculating harmonic source values of the conventional direct current and the flexible direct current at an alternating current side node based on the operation data; and inputting the harmonic source numerical value on the one or more nodes, carrying out load flow calculation based on the harmonic model and the operation data, and generating a calculation result of each harmonic. According to the method, the influence of harmonic waves generated by conventional direct current and flexible direct current in a normal operation state on the power grid can be considered, and the accuracy of large power grid harmonic wave calculation can be improved.

The invention discloses a photovoltaic power station inverter harmonic control method and system, and relates to the technical field of photovoltaic power generation. Comprising the steps of performing harmonic analysis on output of a power grid and an inverter, and establishing harmonic models of the output of the power grid and the inverter; determining harmonic information according to the harmonic model; correcting the harmonic frequency obtained in the harmonic model; setting target control parameters of a filter based on the harmonic information, and filtering; meanwhile, defining a filtering effect, and setting an adjusting period for monitoring a filtering process; and adjusting the target control parameter of the next adjustment period according to the filtering effect of the previous adjustment period. According to the method, harmonic analysis is carried out on the output of the power grid and the inverter, and the harmonic model of the output of the power grid and the inverter is established, so that accurate analysis and modeling of harmonic characteristics are realized, and a reliable data basis is provided for subsequent harmonic control; meanwhile, multiple factors such as power grid fluctuation, inverter characteristics and load influence are considered, and the adaptability of the system is enhanced.

The invention discloses a grid-connected stability analysis method for a multi-converter system, and the method comprises the steps: building a transfer function model from the voltage amplitude-phase disturbance to the power harmonic disturbance of a converter port based on the admittance characteristics of converters, the conversion relation between the voltage / current amplitude-phase disturbance and the positive and negative sequence disturbance, and the power disturbance decomposition relation; simplifying the voltage-power harmonic models of the plurality of converters and connecting lines step by step through series aggregation operation and parallel aggregation operation to generate a grid-connected point single-port voltage-power harmonic transfer function model; and combining the grid-connected point single-port model with a power grid side voltage-power harmonic transfer function model, and judging the system stability according to the origin surrounding property of a Nyquist curve of a joint transfer function determinant.

The application discloses a kind of interval harmonic power flow calculation method using relative distance measure, first input the parameter of power grid and network fluctuation, construct the node admittance matrix of fundamental wave and harmonic, set the RDM initial value of node voltage and carry out fundamental wave power flow iteration calculation, in the process of fundamental wave power flow iteration, the correction of reactive power injection and voltage is carried out to PV node, after meeting convergence condition, the RDM number of the fundamental wave voltage and injection current of whole network is output. After that, the harmonic power flow iteration part in decoupling method is further simplified by using simple solution method. The harmonic current is calculated at harmonic source node in combination with harmonic spectrum, and then the harmonic admittance matrix in RDM form is established based on the harmonic model of each element in the whole network, and the harmonic voltage RDM value of each node is obtained through the harmonic voltage equation. Finally, the interval number is converted through the conversion principle of RDM number, and the harmonic voltage interval range of the whole network is obtained, which can be applied to harmonic analysis and treatment.

Embodiments pertain to methods and system for detecting and / or characterizing at least one object in a scene that is being propelled by at least one rotating device. The methods may include transmitting electromagnetic radiation (EM) into free space towards the scene; receiving, from the scene, EM radiation reflections that are reflected from at least one rotating device of the at least one object that is present in the scene; and processing the reflections to detect, based on harmonic characteristics of the reflected EM radiation, the presence of the at least one object in the scene. In some examples, the methods include processing the reflections to characterize, based on the harmonic characteristics of the reflected EM radiation, the type of the at least one detected object. In some examples, the processing comprises applying an harmonic filter on the reflected EM radiation to detect harmonics of the reflected EM radiation.

The invention discloses an urban community household charging pile harmonic suppression method, which comprises the following steps: S1, collecting voltage and current data of a charging pile under different working conditions, analyzing harmonic generation characteristics, constructing a harmonic mathematical model, and determining typical harmonic frequency and amplitude range; s2, an FPGA real-time data processing architecture is designed according to the harmonic model, a high-speed data acquisition module is established, and real-time acquisition and accurate identification of harmonic signals are realized; s3, on the FPGA platform, based on the real-time harmonic spectrum data, deploying an adaptive harmonic suppression algorithm, dynamically filtering the target harmonic frequency, and reducing the harmonic content; and S4, according to suppression effect feedback, FPGA control parameters are optimized, energy consumption and cost of the device are reduced, and precise and efficient harmonic suppression performance and economical efficiency balance is achieved. The method can ensure that the current waveform of the charging pile meets the power grid standard, remarkably improves the harmonic suppression efficiency and the economical efficiency of the device, and reduces the energy consumption and the equipment maintenance cost.

The invention discloses a fault diagnosis method for a radio frequency front-end circuit of an MIMO system, and the method comprises the steps: carrying out the preprocessing of a collected fault signal through synchronous enhanced extraction transformation; fault features are extracted, a fault discrimination model based on fusion of an asymmetric convolutional neural network of a complex field and a multi-head attention module is constructed, fault feature weight distribution, key feature extraction and fault discrimination are carried out, and a compressed and rearranged time-frequency analysis theory is applied to fault feature extraction. A Gaussian modulation chirp multi-harmonic model is introduced to construct a synchronous enhanced compression feature transformation operator to extract a fault feature component and calculate real domain features and virtual domain features of the fault feature component to obtain a real domain two-dimensional matrix i and a virtual domain two-dimensional matrix q, so that enhanced time-frequency features are obtained; and fault discrimination is converted from a complex field feature space to a high-dimensional space, fault feature weight distribution, key feature extraction and fault discrimination are realized, and finally a fault diagnosis result is output. Experimental results show that the fault diagnosis method for the radio frequency front-end circuit of the MIMO system can accurately extract the characteristics of fault signals and accurately complete fault diagnosis.

The present invention discloses a forest tree species group classification method considering harmonic model coefficients and phenological parameters, comprising the following steps: S1, image acquisition and preprocessing; S2, establishing an MCCDC model based on multi-source remote sensing data; S3, extracting annual forest phenology and MCCDC coefficients based on a logistic regression equation; S4, identifying tree species groups considering phenological parameters and MCCDC parameters. The present invention uses forest phenological parameters extracted from remote sensing and the constructed harmonic model MCCDC coefficients as input variables for tree species classification modeling, providing unique classification data features different from traditional spectral and texture feature methods, compensating to a certain extent for the influence of the phenomena of "same object with different spectra" and "different objects with the same spectra" on the classification accuracy when only relying on spectral and texture feature inputs, thereby improving the classification accuracy of forest tree species (groups).

The application discloses a kind of human activity influence assessment methods of forestry ecological diversity, comprising: the historical remote sensing image sequence of target area is collected, the reflectivity of pixel is fitted as continuous harmonic model;Harmonic model is used to calculate the reflectivity of pixel fitting, and the mutation pixel is screened out, and then the mutation point that human activity produces disturbance to target area is identified;The normalized disturbance index of pixel is calculated, and the habitat suitability index of pixel is obtained;The habitat suitability index of pixel is calculated, and the suitable habitat pixel is screened out, and the maximum activity radius and ecological area of organism in suitable habitat patch are calculated;Ecological diversity influence coefficient is calculated, and the influence situation of human activity on the ecological diversity of target area is evaluated.The application uses long time sequence remote sensing to quantize disturbance and recovery track, can identify short-term interference and long-term recovery process, realize the time sequence correlation evaluation of " change process-ecological response ".It provides data support for forestry sustainable management and ecological protection.

The invention discloses a polar shift forecasting method considering periodic time-varying characteristics, which belongs to the technical field of spatial geodetic survey, is used for polar shift forecasting and comprises the following steps: preparing a data set, constructing a polar shift complex time sequence and adaptively optimizing and determining an optimal periodic parameter by using a differential evolution algorithm. Constructing a complex field harmonic model to calculate a polar shift prediction value, and extrapolating to obtain a fitting prediction value; constructing an autoregression model, and calculating a residual error sequence forecast value; and adding the fitting forecast value and the residual error sequence forecast value to obtain a final polar shift forecast result. According to the method, the time-varying period parameters in the polar shift sequence are adaptively determined by introducing the differential evolution algorithm and the global optimization algorithm, so that more accurate fitting and forecasting of key elements such as the period, the amplitude and the phase change of the Cashler swing and the annual term in the polar shift signal are realized, and a more stable residual sequence is provided for an autoregression model; and the precision and the stability of polar shift, especially medium and long-term span forecasting, are remarkably improved on the whole.

The invention discloses a method for evaluating the influence of human activities on the ecological diversity of forestry, and the method comprises the steps: collecting a historical remote sensing image sequence of a target region, and fitting the reflectivity of pixels into a continuous harmonic model; calculating the reflectivity of pixel fitting by using a harmonic model, screening out abrupt change pixels, and further identifying abrupt change points where human activities disturb the target area; calculating a normalized disturbance index of the pixel to obtain a habitat suitability index of the pixel; calculating habitat suitability indexes of the pixels, screening suitable habitat pixels, and calculating the maximum activity radius and ecological area of organisms in suitable habitat plaques; and calculating an ecological diversity influence coefficient, and evaluating the ecological diversity influence condition of the human activities on the target area. According to the method, disturbance and recovery tracks are quantified by using long-time sequence remote sensing depth, short-term interference and long-term recovery processes can be identified, and'change process-ecological response 'time sequence correlation evaluation is realized. And data support is provided for sustainable management and ecological protection of forestry.

The application discloses a kind of converter harmonic impedance modeling method and related equipment, belong to converter technical field, first obtain grid-connected point voltage and the space vector of current, space vector can accurately reflect the size and direction of voltage and current in real time, compared with traditional scalar modeling, provide more comprehensive information.Harmonic power under positive and negative sequence harmonic influence is sequentially calculated based on space vector, reference voltage after power control loop and harmonic voltage output by inverter, based on inverter side and grid-connected point positive sequence harmonic voltage, negative sequence harmonic voltage and power grid main circuit, the modeling of harmonic impedance model is carried out, the harmonic model of coupling frequency impedance matrix form is used, the interaction relationship between harmonic voltage and harmonic current can be more accurately described, the coupling relationship of different frequency harmonics after converter, so as to improve the accuracy and reliability of analysis result, provide a solid model foundation for harmonic flow research.

The invention belongs to the technical field of permanent magnet synchronous motors, and discloses a resonance-interaction cascade expansion state observer, device and method, and the method comprises the following steps: converting a three-phase stator current into a d-axis current and a q-axis current under a d-q synchronous rotating coordinate system according to a current harmonic model of a permanent magnet synchronous motor; d-axis current and q-axis current are calculated, d-axis voltage and q-axis voltage are calculated, the d-axis current, the q-axis current, the d-axis voltage and the q-axis voltage are injected into the resonance-interaction cascade expansion state observer, and an estimated value and a compensation voltage value of input current are obtained; and injecting the generated compensation voltage value into a vector control current inner ring of the permanent magnet synchronous motor, and adding the compensation voltage value with the d-axis voltage and the q-axis voltage. According to the method, the dynamic performance and the steady-state performance of the system in a small time scale can be improved, the accuracy of the generated compensation voltage can be ensured, the influence of the performance defect of the observer on the current harmonic suppression effect is reduced, and the error of current harmonic tracking is reduced on the premise of ensuring the rapidity.

The invention relates to a harmonic suppression method and system for a road sensing motor. The harmonic suppression method comprises the following steps: constructing a harmonic model corresponding to a six-phase road sensing motor and a transfer function corresponding to a harmonic suppression controller; determining a plurality of harmonic orders corresponding to the six-phase road sensing motor in operation based on a harmonic model; determining a suppression regulation factor corresponding to each harmonic order in the plurality of harmonic orders according to the transfer function; and carrying out harmonic suppression on the six-phase road feeling motor in operation by utilizing a harmonic suppression controller based on the suppression regulation factor corresponding to each harmonic order. In the embodiment of the invention, the optimal suppression effect of the harmonic suppression controller is realized by constructing the harmonic model which is suitable for the six-phase road feeling motor and can identify high-order and low-order harmonics and adjusting the transfer function of the suppression regulation factor in real time, so that the torque ripple and the working noise of the motor are suppressed to the maximum extent; and the working performance of the motor is always kept in an optimal state. In addition, the method can meet the redundant function requirement.

The invention discloses a motor simulator considering motor voltage-current-torque harmonic simulation. The motor simulator comprises a simulation motor electromagnetic harmonic model, a simulation motor motion harmonic model, a voltage modulation optimization model, a connection inductor and an inverter. Wherein the simulation motor electromagnetic harmonic wave model takes a three-phase current and a rotor position as input, and voltage and torque ripple of a simulation port considering harmonic waves are obtained; the simulation motor motion harmonic model takes torque pulsation and simulation load parameters as input to obtain a rotor position considering the rigidity and damping of the dual-mass spring-damping system; and the voltage modulation optimization model converts the voltage of the analog port into a switching signal of the power device. The method aims at solving the problem that in the prior art, due to the fact that inherent harmonic characteristics of the motor are ignored, deviation exists between a simulation result and an actual test, and higher-precision motor simulation and controller test are achieved by establishing the harmonic model accurately reflecting the inherent characteristics of the motor and integrating power level simulation.

The invention discloses an inductance harmonic measurement and analysis method, which is based on an alternating current static measurement method and comprises the following steps of: 1, establishing an inductance harmonic model: respectively constructing a self-inductance model of a stator winding, an inter-phase mutual inductance model and a self-inductance and mutual inductance matrix model of a three-phase winding; 2, an alternating current static measurement circuit is adopted, alternating current with a fixed frequency is introduced into two-phase windings of the motor, a motor rotor is kept static at different space angle positions, and voltage and current parameters between the two phases are measured; step 3, based on a measurement result, calculating to obtain a comprehensive inductance parameter which is LAA-MAB + LBB-MAB and changes along with the rotor position angle theta; and 4, extracting second-order and fourth-order harmonic amplitudes of the inductor to obtain the harmonic content of the inductor of the motor. According to the method, the second-order and fourth-order harmonic amplitudes of the winding inductance of the permanent magnet synchronous motor can be accurately extracted, so that the harmonic content of the inductance of the motor body related to second-order and fourth-order noise is effectively evaluated, and accurate inductance harmonic data is provided for noise optimization of an EPS system.

This invention belongs to the field of harmonic analysis technology and provides a method and system for harmonic modeling of server clusters based on operating condition clustering. It acquires multi-dimensional operating condition parameters of a single server, preprocesses the acquired data, matches the preprocessed data with a preset equivalent operating condition class of server harmonic characteristics, calls the corresponding dedicated harmonic model, and superimposes them to obtain the harmonic model of the server cluster. If the operating condition parameters do not fall within the parameter range of any preset equivalent operating condition class, it is considered a newly added equivalent operating condition class, and the corresponding dedicated harmonic model is fitted to the dedicated harmonic model library. This invention achieves adaptive calculation of the server cluster harmonic model, reduces the computational complexity of the model, and improves the calculation speed and modeling accuracy.

The application discloses a polar motion prediction method considering period time-varying characteristics, belongs to the technical field of space geodetic measurement, and is used for polar motion prediction and comprises the following steps: preparing a data set, constructing a polar motion complex time sequence, and determining optimal period parameters by using a differential evolution algorithm adaptive optimization; a complex domain harmonic model is constructed to calculate polar motion prediction values, and the fitting prediction values are extrapolated; an autoregressive model is constructed to calculate residual sequence prediction values; and the fitting prediction values and the residual sequence prediction values are added to obtain final polar motion prediction results. By introducing a differential evolution algorithm global optimization algorithm to adaptively determine time-varying period parameters in the polar motion sequence, more accurate fitting and prediction of key elements such as period, amplitude and phase change of Chandler wobble and annual term in the polar motion signal are realized, a more stable residual sequence is provided for the autoregressive model, and the accuracy and stability of polar motion prediction, especially medium and long term span prediction, are significantly improved as a whole.

The present application relates to the field of signal processing technology, and in particular to a modeling method, device, electronic device and storage medium for periodic signals, wherein the method comprises: obtaining a coordinate time series of a target navigation satellite system; preprocessing the coordinate time series to obtain a preprocessed coordinate time series, and correcting the preprocessed coordinate time series to obtain a corrected coordinate time series; estimating the corrected coordinate time series to obtain a sine coefficient of the periodic amplitude, a cosine coefficient of the periodic amplitude and a periodic frequency deviation; and decomposing the corrected coordinate time series to establish an initial harmonic model, and using a preset estimation strategy to estimate the parameters to be estimated of the initial harmonic model to obtain an estimation result, so as to establish a final harmonic model based on the estimation result and the initial harmonic model, thereby solving the problem of systematic deviation caused by the empirical period length assumption in coordinate time series modeling, and improving the accuracy of seasonal deformation inversion and the reliability of crustal movement rate estimation.

The invention relates to an M3C double-fundamental-frequency coupling characterization method, device, equipment and medium, and the method comprises the steps: building a basic dynamic equation of bridge arm electrical parameters based on an M3C average value model; based on the basic dynamic equation, performing frequency domain decomposition and matrix representation on the electrical parameters under power frequency and low frequency conditions to generate a two-dimensional frequency domain matrix; performing linear equivalent modeling on the frequency domain operation relation of the two-dimensional frequency domain matrix to obtain a structured matrix; dimensionality reduction processing is carried out on the structured matrix, and steady-state frequency representation of the bridge arm electrical parameters is obtained; and based on the steady-state frequency representation, deducing to obtain a steady-state frequency domain harmonic model of the bridge arm loop. The method has the effect of improving the accuracy of analyzing the steady-state frequency characteristics of the electrical parameters of the bridge arm by the M3C.

The invention discloses a permanent magnet synchronous motor modeling method based on harmonic analysis, and belongs to the technical field of power generation, power transformation or power distribution. The method comprises the steps of obtaining flux linkage data changing along with the position of a rotor under different excitation currents, establishing a flux linkage harmonic model representing a flux linkage as a superposition form of a flux linkage fundamental component and a flux linkage harmonic component, representing the flux linkage harmonic model as a function related to the excitation currents and the position of the rotor, and obtaining a lightweight flux linkage harmonic model. Based on an energy conservation relation between mechanical power and electromagnetic power and the lightweight flux linkage harmonic model, establishing an electromagnetic torque harmonic model which is related to excitation current, a rotor position, the number of magnetic pole pairs and a rotor initial position and is in an analytic harmonic superposition function form; a permanent magnet synchronous motor model is established by combining a lightweight flux linkage harmonic model and an electromagnetic torque harmonic model in a harmonic superposition function form, and the purpose of accurately and efficiently obtaining the torque and flux linkage of the motor under different working conditions is achieved.

The present invention relates to the technical field of the electric power steering system of an automobile, and specifically relates to a rotor flux harmonic d-q modeling method based on a Y-shifted 0° dual-three-phase motor. A rotor flux harmonic d-q modeling method based on a Y-shifted 0° dual-three-phase motor. Compared with the prior art, a rotor flux harmonic d-q modeling method based on a Y-shifted 0° dual-three-phase motor is provided, and an independent fundamental wave and harmonic wave model is adopted to construct a mathematical model of a Y-shifted 0° dual-three-phase permanent magnet synchronous motor based on rotor flux harmonics, revealing the corresponding relationship between the interaction of space-time harmonics in generating motor torque ripple.

The application discloses an airborne air pollution detection method based on harmonic vector change and belongs to the technical field of unmanned aerial vehicle (UAV) pollution detection. The steps are as follows: a harmonic initialization model is constructed, and the cosine, sine function amplitude and the pollution background value baseline of a to-be-detected area are solved to obtain a harmonic model of the to-be-detected area; the measurement value at the current time is obtained through a sensor module; the current time is substituted into the harmonic model of the to-be-detected area to obtain the prediction value at the current time; the abnormality judgment index is obtained based on the ratio method and compared with an abnormality threshold value; when N abnormal time instants are continuously detected, the vector change angle pollution judgment is performed to distinguish the UAV noise influence condition and the air pollution condition. The method provided by the application can more sensitively and accurately judge the pollution condition of the to-be-detected area.

The application relates to a DC power distribution network harmonic modeling method based on a substitution theorem, and comprises the following steps: classifying each key device in a DC power distribution network according to the function of electric energy transformation; processing the input end and the output end of each type of device; writing the state space average equation of each device; obtaining the exponential Fourier coefficients of each variable in the state space average equation and bringing the exponential Fourier coefficients into the state space equation to obtain the harmonic state space model of each type of device, and then converting the frequency domain expression of each variable into a time domain expression through a Fourier series expansion formula; and building a harmonic model of the DC power distribution network according to the substitution theorem. Compared with the prior art, the application adopts a harmonic modeling method to perform harmonic analysis on each variable in the DC power distribution network system, and solves the problem that the harmonic state space modeling method is not suitable for large and complex systems.

The invention provides a switching frequency control method and system of a wind power converter, relates to the field of conversion control of electric energy, and actively predicts the switching frequency of the wind power converter under a series of candidate switching frequencies based on working condition data collected in real time, an accurate loss-junction temperature iterative model, a harmonic model based on a PWM theory and the like. Switching loss of the converter, current total harmonic distortion, DC bus voltage ripple and other key performance indexes. Therefore, the comprehensive performance of each candidate frequency is quantitatively evaluated through a cost function integrating multi-target weight and constraint penalty, so that the switching frequency capable of enabling the overall operation cost of the system to be the lowest is optimized in real time. Through closed-loop control of real-time prediction-quantitative evaluation-optimal selection, the switching frequency can dynamically adapt to the current working condition, the restriction and coupling problems among performance indexes are effectively solved, and the global optimization of the converter is realized.

The invention relates to a method, a system, equipment and a medium for measuring and predicting background harmonics of a regional power grid, and the method comprises the steps: obtaining a topological graph of the regional power grid in the current year, and determining a simulation region of a specific voltage level in the topological graph according to an actual demand; modeling the simulation region based on the power grid circuit data of the regional power grid to obtain an initial harmonic model of the regional power grid; taking the actual measurement value of the harmonic current of the regional power grid in the current year as an initial iteration value, operating the initial harmonic model, and continuously iterating until the harmonic current and the actual measurement value output by model simulation meet a preset error requirement, so as to obtain a harmonic model of a simulation region corresponding to the specific voltage level of the regional power grid in the current year; and adjusting the harmonic model according to the power grid circuit data of the transformed or planned year regional power grid, and calculating the harmonic distribution of any point of the transformed or planned year regional power grid based on the adjusted harmonic model. The method can be widely applied to the field of high-voltage alternating-current network planning and design.