39 results about "Harmonic elimination" patented technology

The invention belongs to the field of sensors and signal processing, and particularly relates to a wavelet kernel scale sensitivity oriented abrasive particle induced voltage signal noise reduction method, which comprises the following steps: acquiring an abrasive particle induced voltage signal, and carrying out harmonic elimination on the abrasive particle induced voltage signal to obtain a preprocessed signal; constructing a wavelet kernel function, and calculating the wavelet kernel function and the preprocessed signal to obtain a kernel scale guiding spectrum; constructing a sparse joint noise reduction model based on the kernel scale guiding spectrum; processing the sparse joint noise reduction model to obtain a convex optimization objective function; solving the convex optimization objective function by combining a self-adaptive step gradient descent method and a self-adaptive iterative shrinkage threshold method to obtain a weight vector representing the distribution of the abrasive particle characteristic signals; carrying out binarization processing on the weight vector representing the distribution of the abrasive particle characteristic signals to obtain a characteristic indication vector; carrying out Hadamard product on the feature indication vector and the preprocessed signal, and then carrying out low-pass filtering to obtain a noise reduction signal; according to the method, the abrasive particle characteristic signals can be self-adaptively subjected to non-destructive enhancement and noise reduction processing in a strong interference environment.

The invention provides a PT ferromagnetic resonance overvoltage suppression system and method based on graded damping. The system comprises a secondary resonance elimination module, the secondary resonance elimination module comprises a three-stage damping branch circuit which is connected in series with an open triangle of a voltage transformer, the three-stage damping branch circuit comprises a first current-sensitive resonance eliminator, a second current-sensitive resonance eliminator and a fixed resistor which are connected in parallel, and a branch circuit of the first current-sensitive resonance eliminator is connected in series with a first switch; a branch of the second flow-sensitive resonance eliminator is connected in series with a second switch, and a branch of the fixed resistor is connected in series with a third switch; the fan is used for carrying out air cooling on the first flow-sensitive resonance eliminator, the second flow-sensitive resonance eliminator and the fixed resistor; and the control module is used for controlling on or off of the first switch, the second switch and the third switch. Resonance early recognition is achieved through transient energy comprehensive criteria, three-level damping dynamic switching and fan intelligent temperature control are combined, and the three core problems of response lag, insufficient heat dissipation and weak self-adaption in ferromagnetic resonance suppression are solved.

The invention provides a primary resonance elimination device of a power distribution network voltage transformer and a management and control method, and relates to the technical field of voltage transformer resonance elimination. The primary resonance elimination device comprises a primary resonance elimination resistor, a primary resonance elimination power electronic device, a standby resonance elimination resistor and a standby resonance elimination power electronic device; the primary resonance elimination resistor and the primary resonance elimination power electronic device are connected in series and then are connected in series between a neutral point of the power distribution network voltage transformer and a ground wire; the standby resonance elimination resistor and the standby resonance elimination power electronic device are connected in series, one end of the standby resonance elimination resistor and the standby resonance elimination power electronic device which are connected in series is connected with a neutral point of the power distribution network voltage transformer, and the other end is grounded; the primary resonance elimination device further comprises a current transformer and a temperature sensor; the temperature sensor is used for monitoring the temperature values of the primary resonance elimination resistor and the standby resonance elimination resistor; the current transformer is assembled on a line where the primary resonance elimination resistor and the standby resonance elimination resistor are grounded together and used for monitoring the value of current flowing through the primary resonance elimination device.

The invention discloses a voltage transformer current-sensitive intelligent resonance elimination device and a fault monitoring method thereof, belongs to the technical field of fault monitoring, and aims to solve the problems that a traditional current-sensitive resonance elimination device is unknowable in state, resonance and instantaneous disturbance are difficult to distinguish, the fault identification precision is low, and the operation and maintenance efficiency is poor. The device comprises a flow-sensitive response module and an intelligent monitoring assembly. The current-sensitive response module comprises a response body and a built-in current sensing element; the intelligent monitoring assembly constructs an associated time sequence data set by collecting a real-time electrical signal and a state signal of the current-sensitive response module so as to judge whether the power grid system enters a resonance state; response signal validity calibration and fault identification operations are executed on the flow sensitive response module by constructing a response feature set; the method comprises the following steps: constructing a monitoring data set, extracting evaluation dimensions to perform performance analysis on a flow-sensitive response module, and generating a performance score of the flow-sensitive response module; response monitoring accuracy and operation and maintenance intelligence are remarkably improved, and accurate research and judgment and intelligent operation and maintenance of the resonance state of the power grid are supported.

The invention discloses a frequency-locked loop of a self-adaptive delay signal elimination filter, which comprises a first filter, a second filter, a Park transformation module, a low-pass filter, an amplitude normalization module, an inverse Park transformation module, a frequency estimation module and a low-pass filter, and is characterized in that the first filter is used for eliminating higher harmonics, the second filter is used for eliminating low-order single harmonics, and the amplitude normalization module is used for normalizing the amplitude of the inverse Park transformation module. A signal passing through the filter is converted into a direct current component under a dq coordinate system through the Park conversion module, high-frequency clutter is filtered out through the low-pass filter, then the signal enters the amplitude normalization module, the signal amplitude is standardized to be 1, the signal is recovered into an alternating current signal through the reverse Park conversion module, the alternating current signal is input into the frequency estimation module, and the frequency estimation module estimates the frequency of the signal. And finally, a stable power grid frequency estimation value is obtained after processing by a low-pass filter. The invention aims to eliminate rounding errors and introduce a novel prefilter with relatively small time delay, so that the dynamic and steady-state performance of the first-order frequency-locked loop is improved.

The invention provides an off-line and on-line collaborative optimization MMC harmonic elimination method for harmonic constraint driving, and relates to the technical field of power electronics, S1, generating a switching angle training set and a parameter fluctuation label through clustering analysis and a differential evolution algorithm according to power grid parameters and MMC operation parameters; and S2, extracting harmonic characteristics by using a harmonic detection technology, predicting a switching angle through a neural network, and outputting a final switching angle in combination with a repetitive control link to realize harmonic suppression. According to the off-line and on-line collaborative optimization MMC harmonic elimination method based on harmonic constraint driving, an MMC under a low level number can always keep a low harmonic content level under the complex conditions of different modulation ratios and access to a new energy field station.

The application discloses a kind of harmonic elimination device with self-monitoring function and monitoring method, it is related to harmonic elimination device technical field, it includes two relevant parallel zinc oxide resistance, temperature acquisition module and controller, each zinc oxide resistance branch is in series with disconnecting switch, the controller can control the closing and opening of disconnecting switch, the temperature acquisition module is used to collect the temperature information of zinc oxide resistance, the output end of zinc oxide resistance is arranged to ground, and current transformer is arranged on the ground line of zinc oxide resistance.The application has the effect of facilitating the performance degradation of harmonic elimination resistance monitoring.

This invention discloses a specific harmonic cancellation pulse width modulation method suitable for digital power amplifiers. It involves fitting a periodic signal f(t) to obtain an approximate function g(t) and performing Fourier analysis to derive the Fourier coefficients b of the current. n Wherein, the Fourier coefficient b n With the switching angle sequence α q 'As a parameter; for the switching angle sequence α q 'Optimization is performed to obtain the optimized switching angle sequence α' q According to α q The corresponding circuit is controlled by pulse width modulation to output a voltage waveform with specific harmonics filtered out. This invention obtains a specific switching angle sequence by establishing and solving a system of nonlinear equations. The output voltage waveform with specific harmonics filtered out is then modulated based on this switching angle sequence. This method can generate the desired frequency domain component and eliminate unwanted harmonics. It is also applicable to the design of multiple H-bridge units. At the same switching frequency, this method can output higher-order harmonics than other modulation methods, thus reducing switching losses. Furthermore, its excellent harmonic suppression performance saves hardware costs.

The invention relates to the technical field of power system overvoltage protection, in particular to an integrated intelligent resonance elimination device and a resonance and inrush current data transmission and analysis method.The integrated intelligent resonance elimination device is characterized in that a primary resonance elimination module is connected with a current sensing module, and the current sensing module and a voltage sampling module are connected with an intelligent processing module; the intelligent processing module is connected with the wireless communication module, and the self-power-taking module is connected with the primary resonance elimination module; the primary resonance elimination module suppresses ferromagnetic resonance; the current sensing module monitors a flowing current signal in real time; the voltage sampling module collects a voltage signal of an open triangular side of the voltage transformer; the intelligent processing module judges a resonance type and a high-voltage inrush current event and generates a corresponding event record; the self-power-taking module is coupled to the primary resonance elimination loop, takes energy from the primary side and converts the energy into stable electric energy; and the wireless communication module uploads the event record to a remote background system. Therefore, the problems of function separation, hidden danger of operation reliability and the like in the prior art are solved.

The application discloses a 10KV resonance identification and harmonic elimination method, comprising the following steps: S1, collecting open delta voltage, and using different scales to carry out wavelet decomposition on the collected open delta voltage to extract signal components of different frequency bands; S2, establishing a signal component maximum absolute value M matrix according to the extracted signal components of different frequency bands; S3, comparing the signal component maximum absolute values of the frequency bands to complete amplitude, frequency identification and harmonic identification of waveform singularity; and S4, calculating to obtain a harmonic elimination condition and a damping resistance. The application can accurately identify resonance and select a harmonic elimination damping resistance, and has sensitivity and reliability for eliminating ferromagnetic resonance of a voltage transformer.

The invention provides a stability analysis precision method based on an improved phase-locked loop MMC impedance model. According to the improved phase-locked loop structure of the integrated harmonic elimination module, the relation between input and output of an improved part is deduced, and a mathematical model is constructed. Vector expressions of bridge arm equivalent capacitor voltage, bridge arm current and sub-module switching coefficients are obtained through Fourier transform, and an MMC frequency domain steady-state model is constructed. And based on a multi-harmonic linearization method, the model is linearized at a steady-state working point, and a main circuit small signal model after disturbance injection is obtained. And meanwhile, mathematical modeling is carried out on the control system to obtain a small-signal model of a sub-module switching coefficient under disturbance. And solving an alternating current side impedance model adopting the improved phase-locked loop by combining the two types of small signal models. According to the impedance model provided by the invention, the influence of n-order harmonics in the modeling process is effectively eliminated, the precision of the impedance model is improved, and a more reliable reference basis can be provided for stability analysis and parameter design of the MMC system.

This application discloses a method for extracting the DC component of an AC signal, comprising: acquiring the AC signal to be processed and its fundamental angular frequency; sequentially performing low-frequency harmonic elimination processing on the AC signal according to the fundamental angular frequency in descending order of harmonic order, wherein each low-frequency harmonic elimination process is configured to: eliminate the current target low-frequency harmonic, while amplifying the high-frequency noise and higher-order harmonics in the AC signal that have not been eliminated, causing the high-frequency noise and higher-order harmonics to trigger amplitude limiting; after completing a preset number of low-frequency harmonic elimination processes, filtering the obtained signal to extract the target DC component from the AC signal; wherein the amplitude limiting value is set to be significantly higher than the amplitude of the target DC component in the AC signal, so that the amplitude of the high-frequency noise and higher-order harmonics after amplitude limiting is far away from the amplitude of the target DC component. This method can achieve fast and accurate extraction of the target DC component.

The application discloses a parallel MPWM modulation method of 3X harmonic elimination, and relates to the technical field of wireless communication.The method comprises the following steps: based on the principle of harmonic elimination, input baseband signals are decomposed into four phase-controlled baseband modulation signals; the baseband modulation signals are subjected to digital up-conversion to obtain intermediate frequency signals; a parallel optimization module is set in a parallel MPWM algorithm, and the intermediate frequency signals are subjected to optimization processing based on the parallel optimization module to obtain four bit pulse sequence codes; the four bit pulse sequence codes are converted into four two-level radio frequency pulse signals; wherein, the sum of the four two-level radio frequency pulse signals is a required five-level radio frequency pulse width modulation signal, the center frequency of the five-level radio frequency pulse width modulation signal is a carrier frequency, and 3X harmonic is eliminated.The application can improve the signal-to-noise ratio, suppress harmonics, and widen the achievable carrier frequency of RF-PWM.

The invention discloses an outdoor high-voltage vacuum switch, which comprises a wire inlet side voltage transformer pre-embedded in a left insulator and a pluggable wire outlet side voltage transformer mounted on a right insulator, an isolating switch chamber is arranged in the right insulator, an observation window is arranged below the isolating switch chamber, and the observation window is connected with the left insulator and the right insulator. The inner wall of the isolation switch chamber is provided with a thin-wall area, the outer side of the isolation switch chamber is provided with a pressure relief port, and the outer side of the left insulator is provided with a resonance elimination resistor or a zero sequence voltage transformer. An external voltage transformer and an external electricity taking transformer are omitted, and the purposes of simple structure, low cost and small size are achieved.

The application relates to a ground current harmonic component interference identification method, which comprises the following steps: a differential circuit is designed based on a cable without defects; the differential circuit is used for defect detection of a cable sample loop; and an output signal of the differential circuit is a harmonic component signal caused by defects after elimination of power supply side harmonic interference. The application constructs a power distribution cable sample loop defect harmonic component detection loop suitable for elimination of power supply side harmonics in a laboratory, can eliminate the influence of power supply side harmonics introduced by a power supply and a through core transformer loop on the power distribution cable sample defect harmonic component detection in the laboratory, and improves the analysis efficiency of test detection data.

The invention discloses a PT protector suitable for a secondary resonance elimination device, and relates to the technical field of power system protection. The PT protector is connected in series between a PT opening secondary winding and a secondary resonance elimination device, and comprises a protection resistor, an alternating current starting type relay, a time relay and an intermediate relay, and all the parts work cooperatively, so that the normal action and the short circuit fault of the secondary resonance elimination device are accurately distinguished, and mistaken cut-off is avoided; and when the working power supply loses power, the current can still be limited through the protection resistor, so that the problem of short-circuit protection deficiency of the secondary winding of the PT opening is effectively solved.

The utility model discloses an electric power resonance elimination device, which belongs to the technical field of electric power system protection, and is characterized in that a control module is arranged in the device, the control module is connected with a voltage detection module and a switch unit, and the voltage detection module is connected with a primary resonance elimination module and a secondary microcomputer resonance elimination module; the primary resonance elimination module is formed by connecting a plurality of resonance elimination action mechanisms in series; the switch unit respectively controls electromagnetic switches in all resonance elimination action mechanisms in the primary resonance elimination module, the secondary microcomputer resonance elimination module mainly consists of a rectifier, an inverter and a resonance elimination resistor which are connected in series, the rectifier is used for carrying out full-wave rectification on network voltage to form direct-current voltage, the inverter is used for inverting the direct-current voltage to alternating-current voltage, and the resonance elimination resistor is used for carrying out resonance elimination on the alternating-current voltage. An inductor connected in series or in parallel with the resonance elimination resistor is driven to work; and the control module determines the on-state of the switch unit by judging the type and amplitude of the output signal of the voltage detection module.

The invention relates to the technical field of voltage transformer ferromagnetic resonance elimination, and particularly provides a voltage transformer resonance elimination device and method based on a current limiting technology. The device comprises a resonance eliminator; the limiting assembly comprises a rotating ring and a plurality of threaded fasteners; the rotating ring is rotatably arranged on the grounding platform; the grounding platform is provided with a plurality of internal threaded holes, and the threaded fasteners are connected with the corresponding internal threaded holes in a matched mode through external threads. The threaded fastener is used for clamping the fixing rod during rotation; the adjusting assembly is used for adsorbing the fixing rod when being electrified, so that the resonance eliminator is grounded; the distance measuring assembly is used for detecting the mounting distance between the fixing rod and the grounding platform; the control device is used for judging whether the resonance eliminator is completely grounded or not based on the installation distance and the preset distance and controlling the limiting assembly and the adjusting assembly to act. According to the voltage transformer resonance elimination device and method based on the current limiting technology, the problem that grounding is incomplete due to the fact that fixing bolts of a resonance eliminator are prone to loosening can be solved.

The application provides a kind of building intelligent system integrated electromechanical equipment control method, it is related to electromechanical equipment control technical field, the present application is based on the harmonic characteristic of electromechanical equipment under the same voltage, the harmonic characteristic table of each electromechanical equipment under different control frequency corresponding harmonic characteristic, based on the harmonic characteristic of each electromechanical equipment, and then analyze its appearance rate, harmonic elimination rate, hazard coefficient, determine the matching priority of each harmonic characteristic, based on the harmonic characteristic table of each electromechanical equipment, obtain the control sensitivity of the electromechanical equipment, and combine the operation stability, and then determine its control post level, based on the control post level of each electromechanical equipment, the matching priority of harmonic characteristic forms matching sequence code, carries out matching and eliminates the harmonic characteristic of harmonic, and judges whether electromechanical equipment needs to be controlled, for the electromechanical equipment needing to be controlled, after adjusting control frequency, carry out secondary matching and eliminate harmonic characteristic.

The invention discloses a resonance elimination device with a self-monitoring function and a monitoring method, and relates to the technical field of resonance elimination devices.The resonance elimination device comprises two zinc oxide resistors which are connected in parallel, a temperature acquisition module and a controller, and the branch where each zinc oxide resistor is located is connected with a breaking switch in series; the controller can control switching on and switching off of the breaking switch, the temperature acquisition module is used for acquiring temperature information of the zinc oxide resistor, the output end of the zinc oxide resistor is grounded, and a current transformer is arranged on a grounding line of the zinc oxide resistor. The application has the effect of conveniently monitoring the performance degradation condition of the resonance elimination resistor.

This application relates to the field of electrical equipment operation control technology and discloses a method for overvoltage identification and current limiting harmonic elimination control of voltage transformers. The invention first acquires multi-source response data within a preset analysis period corresponding to the abnormal triggering time, performs tagging processing on topology state information and thermal state information to generate context labels, and performs standardized characterization and magnetic state proxy conversion on voltage and current responses to generate pre-control standardized observation results, pre-control magnetic state risk quantities and voltage anomaly characterization. Then, it implements restricted diagnostic control actions, and combines the differences in multi-source responses before and after the control actions with the network real anomaly template responses and measurement distortion template responses in the template library to generate observation confidence results and controlled object risk state results, so as to determine the formal control path label and control level.

The embodiment of the invention provides an energy storage centralized commutation system for a thermal power plant and a harmonic elimination method. The system comprises an energy storage unit; a power generation device; the interface unit is used for connecting the power generation equipment; the centralized current conversion unit is respectively connected with the interface unit and the energy storage unit and is used for bidirectional conversion between direct current and alternating current; the acquisition unit is used for acquiring an electric signal in system operation; and a processing unit which is in communication connection with the acquisition unit and the centralized commutation unit. Wherein the acquisition unit is configured to acquire harmonic current components, including an alternating-current harmonic current component and a direct-current harmonic current component, generated in a commutation process, and acquire dq-axis inductance components of a power generation stator of the power generation equipment; and the processing unit is configured to generate an opposite current harmonic frequency by controlling the centralized commutation unit or the energy storage unit based on the data acquired by the acquisition unit so as to eliminate the detected harmonic current.

The invention provides a low-frequency current ripple suppression method and device and a state machine controller, and the method comprises the steps: enabling a system to enter a soft start stage after the system is powered on, opening a main control loop, and closing a harmonic elimination loop; after the soft start is completed, obtaining the input voltage, the output current and the output power of the solar controller; judging whether the system is in a stable state or not according to the input voltage, the output current and the output power; and if it is judged that the system is in the stable state, starting the harmonic elimination loop. The harmonic elimination loop and the main control loop work independently, superposition output is carried out only in a stable state, and coupling of the control loop can be reduced.

The application is suitable for the technical field of multi-level topology harmonic suppression and four-quadrant feedback control, and provides a multi-level topology harmonic suppression and four-quadrant feedback integrated control system and method, which comprises the following steps: S1, system initialization, input parameters, and loading preset parameters; S2, real-time calculation of output voltage harmonic distortion rate THD through fast Fourier transform, harmonic analysis, if the harmonic analysis is greater than 5%, the adaptive harmonic elimination algorithm is activated, and a compensation voltage waveform is generated; S3, separation of active / reactive components through Park transformation, judgment of energy flow direction, and four-quadrant mode switching; S4, the compensation voltage is superimposed on the modulation wave through the improved SVPWM, and then four-quadrant feedback control is carried out; S5, IGBT junction temperature, DC bus ripple, and harmonic spectrum are collected, power grid voltage fluctuation is predicted based on LSTM, and the carrier frequency is dynamically adjusted. The scheme has good harmonic suppression effect, high energy efficiency improvement, fast dynamic response, low maintenance cost, and strong environmental adaptability.

The application belongs to the technical field of flow-sensitive harmonic elimination devices, and particularly relates to a one-time neutral point access type flow-sensitive harmonic elimination device, which comprises a unit composed of PTC thermistors and PPTC thermistors in series, and then connected in parallel with a thin film capacitor and a pressure sensitive resistor, the unit is connected through N series to form a main circuit, the main circuit is connected with a PT one-time neutral point through a wire and the end is grounded; the device further comprises a wiring terminal, a base, a shell, a circuit board and filling glue, the wiring terminal is fixedly connected with the PT one-time neutral point through a screw, the base is fixed on a grounding row, the shell wraps the circuit board, the filling glue is filled in the shell, and the circuit board is integrated with the PTC thermistors, the PPTC thermistors, the thin film capacitor and the pressure sensitive resistor.

The utility model relates to the technical field of harmonic detection, in particular to an integrated plug box and a harmonic elimination monitoring system. The side wall of the accommodating frame is fixedly provided with a connecting assembly; the connecting assembly comprises a voltage and current acquisition port, an input port and an output port. The voltage acquisition loop comprises a clamping protection module and a signal conditioning module and is used for monitoring and inputting real-time voltage; the current acquisition loop comprises a signal conditioning module, a current transformer is connected to one end of the signal conditioning module, and real-time current is monitored and recorded; the input end of the digital-to-analog conversion module is connected to the signal conditioning module, and the output end pin of the digital-to-analog conversion module is connected to the CPU. According to the scheme, allogeneic hanging rail type side wall installation and modular design connection are adopted, the size is reduced by 40%, dense installation is supported, and MTBF is larger than 100,000 hours; the precision is higher, the voltage / current measurement precision reaches 0.5%, the phase error is smaller than or equal to 1 degree, the temperature drift is smaller than 1% of a full scale, long-term monitoring and transient fault capture can be both considered, and accurate analysis after the detection process is finished is supported.

The utility model discloses a bus low residual voltage full frequency limit harmonic PT cabinet control system relates to low voltage circuit protection technical field, including the isolation handcart, high voltage current -limiting fuse and voltage transformer, the positive pole of high voltage current -limiting fuse is connected with low voltage power grid bus, through the active current -limiting harmonic eliminator and microcomputer secondary harmonic eliminator of setting, wherein the primary harmonic elimination of active current -limiting harmonic eliminator can eliminate high frequency resonance voltage, and microcomputer secondary harmonic eliminator can effectively eliminate low frequency resonance voltage, so can realize full frequency limit harmonic function, the resonance elimination and protection effect of this control system to low voltage circuit has been improved to the maximum degree to the active current -limiting harmonic eliminator thermosensitive type harmonic elimination module's resistance value is kiloohm level when normal work, and voltage transformer primary winding's resistance value is megaohm level when normal work, therefore will not produce the influence to each performance of voltage transformer.

The invention discloses a PCS low THD regulation and control method and system based on an optimal switching angle, and relates to the technical field of PCS regulation and control methods, and the method comprises the steps: carrying out the pulse width modulation PWM waveform expansion of N switching angles based on the Fourier series of PCS output voltage, constructing a harmonic mathematical model, optimizing the data in the Fourier series, and listing a nonlinear equation set; solving the nonlinear equation set, constructing a regulation and control model for reducing total harmonic distortion, and obtaining an optimal switching angle sequence under different working conditions; inputting the real-time electrical operation quantity into the trained AI model for processing, outputting an optimal switching angle under a continuous working condition, caching a typical working condition result through an implantation table, calculating the optimal switching angle, and regulating and controlling THD; and taking the regulated THD as an optimization target, carrying out specific gravity distribution and harmonic distribution, arranging a mutual inductance coil in the PCS, and inhibiting current waveform harmonic waves by enhancing magnetic field energy. According to the invention, the harmonic elimination effect of the PCS is improved.

This invention provides a three-level isolation inverter with modulation optimization function, belonging to the field of electronic digital data processing technology. The invention establishes a midpoint potential dataset and a multi-dimensional matrix model by real-time acquisition of system parameters; analyzes the midpoint potential change law based on physical change equations, and constructs a mapping relationship between switching states and midpoint potential changes; identifies load conditions and analyzes outliers to form compensation strategies under special conditions; calculates the impact of dead-zone effects and generates compensation parameters; determines the modulation state and optimizes over-modulation region control; uses a selective harmonic cancellation algorithm to solve for the optimal switching angle sequence; and fine-tunes the harmonic optimization pulse sequence by integrating the midpoint potential variation matrix, compensation matrix, and dead-zone compensation matrix to form the final optimized modulation pulse sequence. This solves the technical problem of output voltage quality degradation caused by midpoint potential fluctuations in existing three-level inverters.

The application discloses an electromagnetic voltage transformer current-limiting and resonance-eliminating device based on PTC characteristics and an optimization method thereof, and relates to the technical field of power protection. The device comprises the following steps: adopting donor doping, acceptor doping and glass phase modification to regulate and control barium titanate-based positive temperature coefficient ceramics to form a positive temperature coefficient core; forming a conductive electrode layer on the positive temperature coefficient core; connecting the positive temperature coefficient core in series according to the number of multiple pieces and in series according to the insulation packaging parameters, and then connecting the positive temperature coefficient core in series between a primary neutral point of a voltage transformer and the ground to form a current-limiting and resonance-eliminating device; and arranging the collected zero sequence voltage and neutral point current according to a unified sampling time mark to form a joint discrimination signal. The application can improve the identification accuracy among frequency resonance, fundamental frequency ferromagnetic resonance, arc grounding and single-phase grounding by first screening abnormal states in layers and then further distinguishing power frequency dominant abnormalities, so that the misjudgment and misoperation are reduced.