293 results about "Total harmonic distortion" patented technology

The invention discloses a three-level inverter dual-tracking model prediction control method and an inverter, and the method comprises the steps: constructing an integral sliding mode observer, and obtaining a current prediction value and a lumped disturbance estimation value through the integral sliding mode observer; calculating a voltage error of the inverter, and substituting the voltage error into the PI controller to obtain a voltage tracking control item; based on the voltage tracking control term, a switching state that minimizes the cost function is selected to control the inverter. The integral sliding mode observer is configured to calculate a current prediction error between a current prediction value of a current control period and a system output current, introduce an integrator to track the current prediction error, and generate an error function based on an output result of the integrator and the current prediction error. And feeding back a current predicted value and a lumped disturbance estimated value of the next control period through an error function. According to the invention, the method can achieve the quick estimation of the operation state of the inverter and the robust compensation of disturbance, reduces the steady-state tracking error, and reduces the total harmonic distortion of the inverter.

The invention relates to the technical field of power system monitoring, and provides a power grid data fault diagnosis method and device based on an intelligent power monitoring instrument, and the method comprises the steps: collecting the operation data of a power grid through the intelligent power monitoring instrument, and generating a fault feature vector containing the multi-dimensional feature parameters of voltage, current and power factor; matching and comparing the feature vector with a preset fault criterion; determining a specific fault type based on a comparison result of the characteristic parameters and a threshold value, including identifying voltage abnormity through a voltage deviation rate, identifying harmonic exceeding through a current harmonic total distortion rate, and identifying a three-phase imbalance fault through a three-phase imbalance degree; for judgment of the three-phase unbalance degree, mean square error statistic calculation is adopted, and a safety coefficient is introduced for threshold comparison; and the fault influence priority is evaluated by quantifying the degree of deviation of each characteristic parameter from the threshold. The fault diagnosis efficiency and reliability can be improved, and intelligent decision support is provided for safe operation of a power grid.

The invention discloses a self-adaptive harmonic current suppression method for harmonic waves of a photovoltaic inverter, which belongs to the technical field of power quality control of a power system and comprises the following steps of: compensating a control strategy through a self-adaptive harmonic component of the photovoltaic inverter by adopting a'detection-reverse injection 'framework; the difference between the residual apparent capacity of the inverter after fundamental wave power supply and the borne harmonic power is used as an adaptive quantity, and the total harmonic distortion rate of the grid-connected point is reduced to the maximum extent on the premise of no overload; the method comprises the following steps: firstly, constructing a real-time harmonic detector based on a cascade generalized integrator; secondly, an inverter impedance model is established from the aspect of impedance stability, and a control parameter stability boundary is determined; then, a self-adaptive harmonic control strategy is introduced into the single-inverter grid-connected system, and a reasonable parameter setting method is provided on the basis of considering stability limitation; afterwards, a capacity-matched harmonic power distribution algorithm is provided for a multi-inverter parallel system, and the efficiency and operation stability of a photovoltaic grid-connected power generation system are improved.

The invention belongs to the technical field of new energy power generation and grid connection, and particularly relates to a wind power plant electric energy quality optimization method and system based on an improved particle swarm algorithm. Aiming at the problems of voltage fluctuation, frequency deviation and high harmonic content during grid connection of a wind power plant, a wind power plant simulation model is built through Matlab / Simulink, a multi-target fitness function is built according to the voltage deviation, the frequency deviation and the total harmonic distortion (THD), the self-adaptive inertia weight and learning factors of a particle swarm optimization algorithm are improved, and a wind power plant grid connection model is built. And dynamically adjusting voltage adjustment gain, reactive compensation amount and filter parameters. According to the embodiment, compared with a traditional method, the number of iterations is reduced by 40%, the voltage fluctuation suppression ratio is improved by 10%, the frequency adjusting time is shortened to be within 0.3 second, the THD is reduced to 2.1% from 5.2%, and the power grid stability and the electric energy quality are improved.

The invention discloses an electric energy meter abnormal phenomenon automatic detection and identification method and system, and relates to electric digital data processing, and the method comprises the steps: carrying out the digital signal processing of initial data, the voltage effective value, the total harmonic distortion rate and the analysis of communication message abnormal codes, and generating a structured feature matrix; on the basis of the structured feature matrix, threshold comparison, composite condition judgment and continuous anomaly detection are executed through multi-level rule triggering, and an anomaly event report is generated; comparing the abnormal event report with a historical case, obtaining the similarity between the current abnormal event report and the historical case, and obtaining a similarity TOP-N case set; generating an anomaly diagnosis report by using weighted evidence fusion in combination with rule triggering intensity quantification and case matching credibility conversion; and updating the case library according to the abnormality diagnosis report, and counting and adjusting a rule threshold based on a sliding window. According to the method, the abnormal judgment threshold values of key parameters such as voltage and harmonic waves can be adjusted in real time through dynamic threshold value optimization, and the adaptability is improved.

The embodiment of the invention provides an excitation signal generation method and system and a digital eddy current sensor, and the method comprises the steps: outputting a square wave signal through a pulse width modulation assembly of a microcontroller unit, and enabling the frequency and resolution of the square wave signal to be adaptive to eddy current probes with different inductance values; inputting the square wave signal into a low-pass filter for filtering, and setting the cut-off frequency of the low-pass filter, the suppression times of higher harmonics and the attenuation slope so as to output a sine wave signal with a target total harmonic distortion range; the amplitude of the sine wave signal is collected in real time, and the pulse width modulation duty ratio and the passband gain of a low-pass filter are dynamically adjusted in combination with a digital control algorithm, so that the sine wave signal is subjected to self-adaptive adjustment and correction and is output; and taking the sine wave signal as an excitation source of an eddy current probe, and driving the eddy current probe to carry out nondestructive testing. According to the invention, the excitation signal which gives consideration to high-frequency signal generation, deep harmonic suppression and digital adaptive adjustment can be generated.

The invention relates to the technical field of electric power system control, and discloses an electric power system arc harmonic collaborative suppression and intelligent closed-loop control system, which comprises the steps of: acquiring sensor data and uploading the sensor data to an edge computing unit by deploying a sensor; wavelet threshold denoising and electromagnetic interference compensation are adopted; the method comprises the following steps: constructing a coupling model containing arc plasma dynamic resistance, optimizing VMD parameters through PSO, extracting a joint feature vector, filling an arc and harmonic dynamic coupling analysis gap, calculating a total harmonic distortion rate and arc extinction time in combination with a power grid damping ratio, solving an optimal SVG trigger angle, and solving the problem of lack of power grid stability evaluation; correcting the opening time of the circuit breaker, calculating the error of the total harmonic distortion rate and the error of the arc extinction time, and adjusting the SVG trigger angle; calculating the precision of the evaluation model, calculating the full life cycle through the aging coefficient, analyzing and judging whether an early warning signal is generated or not, and triggering equipment replacement early warning based on the generated early warning signal.

The invention provides a single-phase four-quadrant rectifier IGBT open-circuit fault diagnosis method under multiple working conditions, and relates to the technical field of IGBT fault diagnosis. Historical data of alternating current side voltage, alternating current side current and direct current side voltage of the single-phase four-quadrant rectifier are obtained, and a total harmonic distortion rate threshold value, a direct current side voltage threshold value and an alternating current side current first threshold value are obtained. And constructing and training an IGBT open-circuit fault positioning identification model. Detecting the total harmonic distortion rate of the alternating-current side current of the single-phase four-quadrant rectifier in real time, if the total harmonic distortion rate exceeds a threshold value, entering fault positioning, collecting and calculating the average value of the direct-current side voltage and the alternating-current side current in the period, and judging the fault of the single-phase four-quadrant rectifier under the specific working condition according to the comparison of the average value and the threshold value. Or using an IGBT open-circuit fault positioning identification model to diagnose the fault; if the threshold value is not exceeded, the next period is continuously monitored. According to the invention, the IGBT fault diagnosis efficiency and accuracy of the single-phase four-quadrant rectifier are improved.

The embodiment of the invention discloses a collaborative optimization method and device for the power quality of a high-permeability transformer area. The method comprises the following steps: acquiring three-phase voltage, three-phase current and environment temperature data; the voltage deviation, the three-phase unbalance degree, the total harmonic distortion rate and the reactive vacancy of the high-permeability transformer area are calculated based on the three-phase voltage and the three-phase current; taking voltage deviation as a primary optimization target, considering optimization of three-phase unbalance degree, total harmonic distortion rate and reactive vacancy, constructing a multi-target optimization function, and carrying out dynamic constraint on an optimization process based on environment temperature data; solving the multi-objective optimization function by adopting an optimization algorithm to obtain a group of optimal decision variables, and converting the decision variables into corresponding control instruction sets; and the control instruction set is issued to the on-load voltage regulating transformer, the reactive compensation equipment and the power electronic compensation module for execution. Therefore, the problems of voltage out-of-limit, harmonic pollution and imbalance are effectively solved through a multi-target cooperation and temperature self-adaption mechanism.

The invention discloses a real-time noise reduction method and system supporting Bluetooth audio interaction, and the method comprises the steps: collecting an environment audio signal and a Bluetooth interaction audio signal, and carrying out the timestamp alignment and spatial calibration of the environment audio signal and the Bluetooth interaction audio signal; an improved multivariate variational mode decomposition algorithm is adopted to decompose and extract noise features, the noise features are combined with user historical noise data, a dynamic noise model is constructed through a long-short-term memory network, parameters are updated in real time, Bluetooth interaction audio content features and a user behavior data recognition scene are analyzed, and a noise reduction strategy is determined. And according to the dynamic noise model and the scene result, reinforcing learning to optimize filter parameters, generating a directional anti-noise signal to carry out noise reduction on the Bluetooth interaction audio signal, collecting the noise reduction intensity manually adjusted by a user, calculating voice definition and total harmonic distortion, and carrying out noise reduction on the Bluetooth interaction audio signal. And inputting a feedback and evaluation result into the modeling and noise reduction steps, carrying out dynamic range adjustment, sound channel balance and power amplification on the audio after noise reduction, and outputting the audio through a loudspeaker.

The application discloses a kind of water electrolysis hydrogen production rectifier transformer harmonic active inhibition optimization method, comprising the following steps: constructing rectifier circuit, rectifier circuit includes switch tube, the voltage vector and zero vector of switch tube output are combined, and combined output voltage vector is obtained;The harmonic amplitude is obtained by processing combined output voltage vector, Levy tangent flight strategy and confidence domain variation strategy are introduced in black-winged kite optimization algorithm to construct improved dynamic search algorithm, the total harmonic distortion is obtained by iterative calculation of harmonic amplitude by improved dynamic search algorithm, i.e. optimal switch tube combination, the switch tube of rectifier circuit is adjusted by optimal switch tube combination, and the total harmonic distortion of rectifier circuit is reduced.The optimal switch tube combination of rectifier circuit is iteratively calculated by improved dynamic search algorithm in the application, effectively reduces resource consumption, and processing speed is accelerated, and the efficiency and accuracy of electrolytic water hydrogen production rectifier are improved.

The invention relates to the technical field of supervision control, in particular to a new energy storage optimization control method and system, and the method comprises the following steps: collecting a grid-connected point voltage amplitude deviation, a frequency deviation and a voltage total harmonic distortion rate, and generating a power grid stress index; according to the method, the multi-dimensional state vector is constructed by collecting the grid-connected point voltage amplitude deviation, the frequency deviation and the total harmonic distortion rate to generate the stress index reflecting the power grid operation pressure, accurate quantitative sensing of the power grid state is achieved, the power grid supporting gain coefficient is dynamically generated according to comparison of the index and the preset threshold value, and the power grid supporting effect is improved. And the total required power to be responded by the energy storage system is adjusted and determined, so that the power support strength is matched with the actual demand of the power grid, and insufficient response or excessive response is avoided.

The invention discloses a three-phase uninterruptible power supply device and a control method thereof. The control method comprises the following steps: acquiring an input current of a three-phase alternating current power supply and a load voltage and a load current of an output end of an inverter circuit; carrying out harmonic separation on the collected input current, and determining a total harmonic distortion rate; when the total harmonic distortion rate is greater than a preset total harmonic distortion rate threshold value, generating a harmonic compensation signal; calculating load variation and voltage deviation based on load voltage and load current, dynamically adjusting proportional gain and integral time in real time, and generating a fundamental voltage control signal; superposing the fundamental wave voltage control signal and the harmonic compensation signal to generate a preliminary modulation wave; dynamically adjusting the dead zone time of the PWM wave, and combining the dead zone time with the preliminary modulation wave to generate the PWM wave; according to the control method, the three-phase alternating current is converted into the alternating current meeting the load requirement through the PWM waves, the response capacity to voltage sag, voltage fluctuation and harmonic disturbance is improved, and the output electric energy quality is improved.

The present application discloses a method, apparatus, device and storage medium for cross-correlated harmonic control in power grids. The method includes: performing wavelet packet decomposition on subnet electrical signals to obtain the harmonic components of the subnet in each frequency band; calculating the harmonic phase difference between subnets based on the cross-correlation function and topological impedance matrix between the harmonic components of each subnet, and calculating the total harmonic distortion rate based on the harmonic components of the subnet in each frequency band; constructing a harmonic transfer equation based on the harmonic phase difference between subnets and the equivalent output impedance of the inverter to calculate the harmonic responsibility ratio of the subnet; solving a two-layer game model based on the total harmonic distortion rate and its reference value and the harmonic responsibility ratio of the subnet to obtain the output of the control equipment; inputting the output of the control equipment into the fuzzy controller to obtain the impedance adjustment amount of the subnet, and adjusting the virtual impedance according to the impedance adjustment amount to update the harmonic return path. The present application realizes the harmonic control between multiple subnets during high-penetration distributed grid connection, thereby improving the stability of power grid operation.

The invention discloses an electric energy quality comprehensive monitoring method and system based on real-time waveform analysis. The method comprises the following steps: S1, acquiring an analog voltage signal acquired by a mutual inductor; s2, preprocessing to obtain a voltage waveform data segment; s3, performing multi-dimensional feature extraction to obtain a voltage waveform multi-dimensional feature vector; s4, extracting a voltage RMS effective value, a total harmonic distortion rate and wavelet packet energy; s5, inputting the voltage RMS effective value, the total harmonic distortion rate and the wavelet packet energy into a grading event pre-detection model to obtain an event feature subset coding vector; and S6, enabling the event feature subset coding vector to pass through an intelligent event fine classification model to obtain an electric energy event accurate classification result. According to the electric energy quality comprehensive monitoring method and system based on real-time waveform analysis disclosed by the invention, the accuracy and efficiency of electric energy quality event monitoring are greatly improved.

The invention discloses a multivariable model predictive control method for a photovoltaic inverter grid-connected system, which comprises the following steps of: establishing a mathematical model of an inverter under a rotating coordinate system, and setting a discrete mathematical model on the basis of traditional model predictive control to obtain a predictive value of output current; and taking the predicted value, the current error at the sampling moment and the error of the direct current bus voltage as control factors of the value function, and seeking the minimum solution of the value function to achieve the optimal control effect. According to the multivariable model predictive control method for the photovoltaic inverter grid-connected system, through the steps, the photovoltaic grid-connected response efficiency can be improved, the total harmonic distortion rate can be reduced, the stability and the anti-interference performance of the direct-current bus voltage can be enhanced, the grid-side current can be controlled at a lower total harmonic distortion level, and the effect is obvious.

The invention discloses an ultra-high heart rate electrocardio acquisition system, which comprises a signal acquisition unit adopting an ADS131E08 chip and supporting 8 channels, a 24-bit delta-sigma ADC (Analog to Digital Converter) and programmable gain amplification; the dynamic sampling rate adjusting unit is used for dynamically adjusting the sampling rate between 1kSPS and 64kSPS according to the heart rate change, and the sampling rate is increased to be greater than or equal to 2kSPS when the heart rate exceeds 200 times per minute; a low-noise design circuit has a common-mode rejection ratio greater than or equal to 110dB, a dynamic range greater than or equal to 118dB and total harmonic distortion less than or equal to-90dB, and power frequency interference is suppressed; the morphological enhancement module is used for enhancing QRS wave group characteristics by using digital morphological filtering; the multi-lead fusion module is used for fusing multi-lead signals through time sequence alignment and R-wave phase difference analysis; and the anti-interference module is integrated with a hardware comparator, and is used for lead falling detection and dynamic digital notch filtering. The system is suitable for researches on myocardial ischemia, arrhythmia and drug cardiotoxicity. Compared with the prior art, the device has the advantages of being simple in structure, low in cost, high in precision, high in reliability and the like, and can effectively solve the problem of animal ultrahigh heart rate electrocardio collection.

The invention discloses a spherical simplex robust unscented Kalman filter and a PWM (Pulse Width Modulation) rectifier control method and device, which are characterized in that (2n + 1) Sigma points in standard unscented Kalman filtering are replaced by (n + 2) simplex vertexes which are symmetrically distributed on a unit hyper-sphere, so that the calculation complexity is remarkably reduced. A covariance matrix and a state quantity are dynamically adjusted in combination with a corrected observation noise covariance matrix and an adaptive factor adjustment mechanism, so that the estimation precision of the filter on the lumped disturbance quantity is remarkably improved, and the robustness and the tracking performance of the system on non-Gaussian noise and abnormal observation values are enhanced. And estimating the lumped disturbance quantity of the system in real time through spherical simplex robust unscented Kalman filtering, introducing the lumped disturbance quantity into a cost function for optimization solution, and selecting an optimal voltage vector to control the on-off state of the rectifier. According to the invention, the total harmonic distortion rate of the output current and the voltage fluctuation of the direct-current bus are obviously reduced under the steady-state condition, and higher response speed and stronger anti-interference capability can be shown under the dynamic working condition.

The invention relates to a distortion degree measuring system and method based on correlation operation, and the system comprises a signal source which is a to-be-measured signal source for outputting a mixed waveform comprising a fundamental wave and each harmonic component; the fundamental wave extraction module is used for separating and extracting a fundamental wave component of which the waveform is a single-frequency square wave from the signal to be detected; the phase-locked loop frequency multiplication module is used for receiving the fundamental component and locking and extracting a sine wave signal containing the fundamental component and a harmonic component through a phase-locked loop containing a programmable frequency divider; the correlator module is composed of a multiplier circuit and a low-pass filtering and amplifying circuit, receives a to-be-measured signal serving as an input signal and a sine wave signal serving as a reference signal, and outputs a direct-current component; and the single chip microcomputer is configured with the programmable frequency divider, samples the direct current component output by the correlator module, calculates the relative amplitude and the total harmonic distortion degree of the fundamental wave component and the harmonic component, and outputs the total harmonic distortion degree. The beneficial effects are that the measurement system and the signal processing method are suitable for signal harmonic analysis under a complex harmonic environment and a low signal-to-noise ratio condition, a high-performance processor and a computing power requirement are not needed, and the system takes an analog circuit as a main body and has the advantages of high measurement speed, high accuracy, low system cost and the like.

This invention discloses a multiplexing configuration method and apparatus for a diode phase-shift rectifier power transmission system, relating to the field of power electronics technology. The method involves acquiring the topology diagram and rectification operating parameters of the diode rectifier unit in the diode phase-shift rectifier power transmission system. Based on the rectification operating parameters and a preset power frequency cycle coefficient, the DC-side output current of the diode rectifier unit is determined. Harmonic characteristic analysis is performed using the DC-side output current and the diode rectifier unit topology diagram to obtain the total harmonic distortion (THD) function corresponding to the diode phase-shift rectifier power transmission system. Based on preset harmonic distortion limits and the THD function, the target multiplexing number of the diode phase-shift rectifier power transmission system is determined. This invention solves the technical problem that existing technologies do not fully utilize the operating parameters of the diode phase-shift rectifier power transmission system to analyze the multiplexing number, thus reducing the reliability of offshore power transmission platforms.

The invention relates to the cross technical field of computer-aided engineering and audio equipment design, discloses a circuit design simulation-based disc player design optimization method and system, and aims to solve the problem that the existing disc player design depends on physical prototype trial-manufacture and subjective listening evaluation and lacks multi-physical domain co-simulation capability. The method comprises the following steps: constructing a unified multi-physical domain model comprising a mechanical transducer, an electromechanical transducer and an electronic circuit sub-model; bidirectional coupling co-simulation based on the time sequence is executed, and an output electric signal is generated; extracting objective audio performance indexes such as total harmonic distortion and signal-to-noise ratio; and carrying out multi-objective optimization on the key design parameters by utilizing a genetic algorithm, and outputting a Pareto optimal scheme. The system comprises a model construction module, a co-simulation module, a performance index extraction module and an optimization module. Through high-fidelity full-link simulation and automatic optimization, the design efficiency and the audio fidelity are remarkably improved, and the research and development cost is reduced.

The invention provides a fault identification method and system for connection of a charging pile to a low-voltage power distribution network, and relates to the technical field of electric vehicle charging, and the method comprises the steps: obtaining charging process data after the charging pile is connected to the low-voltage power distribution network, including the load of a DC charging pile and the total harmonic distortion of three phases of a power grid side; inputting the charging process data into a fault identification integrated model constructed based on an integrated bagging method to obtain a fault type; wherein the integrated bagging method is a bagging method adopting feature randomness, a sample set representing different fault scenes is generated based on a comprehensive sample set, a plurality of classifiers are trained, the trained classifiers are integrated, and a fault identification integrated model is obtained; according to the method, the feature randomness bagging method is adopted, the fault identification integrated model is constructed, the abnormal condition possibly causing the fault in the operation process of the charging pile is identified, and the fault detection accuracy is remarkably improved.

The invention discloses a charging and discharging intelligent management system based on linkage of a BMS (Battery Management System) and an EMS (Energy Management System), which relates to the technical field of energy cooperative control and comprises the following steps: acquiring energy cooperative control data through the BMS and the EMS and preprocessing the energy cooperative control data; constructing a joint impedance model, inputting the preprocessed energy cooperative control data into the joint impedance model, and generating a joint state vector including an optimal matching frequency, a total harmonic distortion rate, battery charge state data and a harmonic suppression weight; and constructing a charging and discharging instruction generation model, inputting the joint state vector into the charging and discharging instruction generation model, and generating an optimal charging and discharging strategy instruction through a strategy generation layer and a decision optimization layer. According to the method, accurate cooperative control of the dynamic characteristics of the battery and the power grid is realized by constructing the combined impedance model, the prediction precision of power grid fluctuation and battery state change is improved, harmonic interference between the power grid and the battery is remarkably reduced through dynamic optimization of the harmonic suppression weight, the service life of the battery is prolonged, and the compatibility of the power grid is enhanced.

The invention discloses an electric equipment monitoring protection method and device. The protection method comprises the following steps: collecting current and voltage data of electric equipment, generating a current and voltage waveform curve based on the current and voltage data, calculating to obtain current and voltage total harmonic distortion, and calculating to obtain current power and current time slope based on the current and voltage data; based on the current and voltage total harmonic distortion and the set current and voltage standard total harmonic distortion, current and voltage harmonic deviation values are obtained through calculation, electric energy quality abnormity is identified according to the current and voltage harmonic deviation values, and an alarm or prompt is given out; on the basis of the magnitude relationship between the voltage waveform curve and a set fundamental wave rated signal in a preset proportion range, identifying voltage abnormity and sending out voltage abnormity early warning or line fault early warning; and calculating a deviation value between the current power and the normal power corresponding to the current state of the electric equipment, and combining the current time slope to identify power abnormality and give an alarm. According to the invention, various abnormal states of the electric equipment can be identified and warned.

The invention discloses a permanent magnet synchronous motor model prediction control method based on multi-target Pareto optimum, which comprises the following steps: measuring two-phase current, motor rotating speed and rotor position of a permanent magnet synchronous motor, converting the two-phase current into d-axis current and q-axis current according to the rotor position, and converting an alternative voltage vector of an inverter into d-axis voltage and q-axis voltage at the same time; inputting the d-axis current, the q-axis current, the d-axis voltage, the q-axis voltage and the rotating speed of the motor into a current prediction model of the permanent magnet synchronous motor, and predicting a future current state value; establishing a multi-target optimization model including torque ripple, current total harmonic distortion, switching frequency and power loss, calculating by using a multi-target particle swarm algorithm in combination with non-dominated sorting and congestion distance to obtain a Pareto optimal solution set, obtaining an optimal weight factor, and automatically adjusting target weights according to motor operation states under different operation conditions; and constructing a cost function based on the optimal weight factor, and selecting a voltage vector enabling the cost function to be minimum as optimal control output.

The application discloses a single-stage three-phase high-frequency isolation type conversion circuit and a closed-loop control method. The single-stage three-phase high-frequency isolation type conversion circuit generates a modulation ratio and a vector angle on the basis of synchronous control of a fundamental wave and a harmonic wave of a three-phase current based on three-phase voltage of a three-phase three-wire power grid and the three-phase current of the three-phase three-wire power grid, generates a primary side driving signal and a secondary side driving signal according to the modulation ratio and the vector angle, the primary side driving signal is used for driving a three-phase matrix converter, and the secondary side driving signal is used for driving a full-bridge inverter. The fundamental wave and the low-frequency harmonic wave of the power grid current can be synchronously controlled, low-order harmonics can be eliminated, the sinusoidal degree of the grid-connected current can be improved, and thus the quality of the power grid current and total harmonic distortion can be improved.

The invention provides an alternating-current side third harmonic weakening modulation method of a railway power regulator under the condition that direct-current bus voltage contains frequency doubling ripples. The method comprises the following steps: constructing a bus voltage state space model of the railway power regulator, and designing a non-delay adaptive state observer to extract direct current component information of bus voltage; separating information of a direct current component and a double frequency ripple component of the bus voltage through a self-adaptive state observer; introducing the direct-current component information into voltage and current double-closed-loop control; designing a secondary pulse modulation ratio opposite to a ripple voltage phase through the extracted ripple pulse parameters; the third harmonic on the alternating current side of the RPC is weakened by injecting an opposite pulsation modulation ratio into a modulation coefficient; according to the method, under the condition that circuit topology and control strategy complexity are not increased, output voltage third harmonics are effectively weakened, direct current side voltage double frequency fluctuation is reduced, meanwhile, power coupling between the alternating current side and the direct current side can be compensated, the requirement for the capacitance value of a bus capacitor is reduced, the total harmonic distortion rate is reduced, and the service life of the bus is prolonged. And long-term stable operation of the system is guaranteed.

The invention relates to the technical field of semiconductors, in particular to an MEMS micro loudspeaker packaging structure and a preparation method thereof, and the packaging structure comprises a substrate which is provided with a hollow cavity structure, a limiting device and a plurality of vent holes in the bottom; and the MEMS sound production chip is inversely arranged on the substrate, and the edge area of the MEMS sound production chip is bonded with the substrate through the connecting part. According to the packaging structure of the MEMS micro loudspeaker provided by the invention, the MEMS sound production chip is inversely arranged and is in direct contact with the substrate used for packaging, so that the packaging structure has higher impact resistance, the inversely arranged MEMS sound production chip can better dissipate heat, and a double-sound-cavity structure in the packaging structure increases system damping and reduces the quality factor of device resonance; the stability and reliability of the chip can be improved, the design of multiple vent holes is combined with the limiting device, the nonlinear displacement of the MEMS sound production chip under the resonant frequency is effectively inhibited, and the total harmonic distortion is reduced.

A harmonic modeling method of a power amplifier solves the problem that a traditional modeling method is not suitable for harmonic modeling analysis of a high-switching-frequency topological structure, and comprises the following steps: obtaining baseband harmonic and sideband harmonic caused by modulation nonlinearity according to the number of parallel half bridges, a modulation wave function and a carrier function in the power amplifier; according to the topological structure of the power amplifier, obtaining a circuit equation of the topological structure in the dead-zone time period; calculating the current amplitude envelope of the resonant inductor; and calculating a voltage error caused by the dead-zone time period according to the calculated current amplitude envelope in combination with a circuit equation of the dead-zone time period, performing Fourier decomposition on the voltage error to obtain distortion harmonics caused by the dead-zone time period of the power amplifier, and obtaining total harmonics in combination with the obtained baseband harmonics and sideband harmonics. According to the invention, the switching frequency when the total harmonic distortion is the lowest can be obtained through modeling.

A multi-source inverter (MSI) topology features significant advantages over conventional MSI converters such as NPC-based and T-Type-based topologies, including a lower number of switching devices, higher efficiency, and better thermal distribution of switching devices. A space vector modulation (SVM) scheme for MSI topologies presented herein and for conventional MSI topologies uses three or four adjacent vectors to generate a reference voltage vector, resulting in lower voltage and current total harmonic distortion (THD) at the MSI output, a lower switching frequency, and increased efficiency relative to conventional MSI modulation. Embodiments are suitable for use in electric vehicles and energy storage systems.