1704 results about "AC - Alternating current" patented technology

A display device is provided, which includes a display panel. The display panel includes a first substrate, a second substrate, a cholesteric liquid-crystal (ChLC) layer, and a driving circuit section. A plurality of first electrodes formed on the first substrate extend in a first direction. A plurality of second electrodes formed on the second substrate extend in a second direction different from the first direction. The ChLC layer is formed between the first substrate and the second substrate. The driving circuit section is configured to apply a plurality of alternating-current (AC) voltage pulses to pixel circuits at intersections between the first electrodes and the second electrodes. The driving circuit section is further configured to perform a full screen reset procedure to the display panel followed by a pulse-width modulation (PWM) scanning procedure to control cholesteric molecules within the pixel circuits to enter a focal conic state.

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 invention belongs to the cross technical field of biomedical engineering and nerve regulation technology. According to the brain-heart linkage transcranial strong alternating current stimulation feedback control method and system, heart rate variability characteristics are obtained according to electroencephalogram signals, electroencephalogram signal characteristics are obtained according to the electroencephalogram signals, and a dynamic coupling index is determined according to the electroencephalogram signals and electrocardiosignals; when the heart rate variability characteristic is greater than or equal to a corresponding heart rate characteristic baseline threshold value, the electroencephalogram signal characteristic is greater than or equal to a corresponding electroencephalogram characteristic baseline threshold value, and the dynamic coupling index is greater than or equal to a set threshold value, judging that the emotional disorder is improved, and keeping the intensity of the stimulation current unchanged; otherwise, increasing the intensity of the stimulation current to a set threshold value until the emotional disorder is improved. Through combined calculation of the electroencephalogram signals and the electrocardiosignals, dynamic monitoring and accurate evaluation of the process of treating the emotional disorder through transcranial strong alternating current stimulation are achieved, and the accuracy of electrical stimulation is guaranteed.

The invention discloses a magnetofluid type silicon controlled rectifier radiator and a heat dissipation control method thereof. The radiator comprises a silicon controlled rectifier, a magnetic fluid chamber is attached to the outer side of the silicon controlled rectifier, the magnetic pole array is installed in the magnetic fluid chamber, and cooling fins are assembled outside the magnetic fluid chamber. When alternating current is introduced into the cavity where the magnetic fluid liquid chamber is located, the alternating current and the magnetic field interact to generate Lorentz force, the Lorentz force drives the magnetic fluid to form directional eddy current so as to achieve convective heat exchange on the silicon controlled rectifier, and heat absorbed by the magnetic fluid and air are subjected to heat exchange through the cooling fins. Junction temperature out-of-control caused by local hot spots of the silicon controlled rectifier can be solved, secondary damage of mechanical vibration of a heat dissipation system to welding spots is eliminated, and the highest junction temperature area of the silicon controlled rectifier is focused and cooled according to needs.

Provided are a detection method, a control device, a power distribution box, and a storage medium. The detection method applied in a power distribution box includes: obtaining a real-time input alternating-current voltage and a zero-point alternating-current phase of the power distribution box within a utility power cycle; obtaining a simulated input alternating-current voltage of the power distribution box within the utility power cycle based on the zero-point alternating-current phase; determining that the real-time input alternating-current voltage is normal in response to an alternating-current voltage difference between the simulated input alternating-current voltage and the real-time input alternating-current voltage being smaller than or equal to a predetermined threshold, or determining that the real-time input alternating-current voltage is abnormal in response to the alternating-current voltage difference between the simulated input alternating-current voltage and the real-time input alternating-current voltage being greater than the predetermined threshold.

An AC series arc detection method, system and device and a readable storage medium relate to the technical field of electrical engineering, and specifically comprise the following steps: generating a current anomaly event and a corresponding current anomaly time window based on a current signal at a current sampling moment and a current signal at a previous sampling moment; the current abnormal events comprise current short-time sudden change abnormity, high-frequency energy sudden increase abnormity and intermittent conduction interruption abnormity; generating a voltage abnormal event and a corresponding voltage abnormal time window according to all voltage signals in the current abnormal time window and the voltage signal at the current sampling moment, wherein the voltage abnormal event comprises zero-crossing conduction abnormity and voltage transient amplitude abnormity; determining a current and voltage dual-channel abnormal event based on the current abnormal time window and the voltage abnormal time window in a preset time alignment window; and determining an alternating-current series arc event according to the current-voltage dual-channel abnormal event to realize alternating-current series arc detection. According to the invention, the accuracy and realizability of alternating-current series arc detection can be ensured.

The present disclosure relates to a standby power supply, including: a first sub power supply configured to provide alternating current electrical energy, where the first sub power supply is connected to an input terminal of an alternating current / direct current (AC / DC) converter; the AC / DC converter configured to convert the alternating current electrical energy into direct current electrical energy, where an output terminal of the AC / DC converter is connected to an output terminal of the standby power supply; and second sub power supplies configured to provide the direct current electrical energy, where the second sub power supplies are connected to the output terminal of the standby power supply. Through the present disclosure, a standby power supply solution having high reliability and capable of meeting power consuming requirements of a load with a great change in power demand such as a wind generator may be provided.

A scan driving method for rendering a high-contrast image, for use in a cholesteric liquid-crystal display device, is provided. The cholesteric liquid-crystal display device includes a display panel and a driving circuit section. The method includes: utilizing the driving circuit section to sequentially activate each scanning electrode using a modified pulse-width modulation (PWM) scanning procedure including a first stage, a second stage, and a third stage in sequence; and utilizing the driving circuit section to apply one or more alternating-current (AC) voltage pulses to pixel circuits on a first scanning electrode during the first stage to manipulate grayscale values of the pixel circuits thereon to be written in the second stage. During the first stage of the first scanning electrode, the pixel circuits on the remaining scanning electrodes within the third stage sense a zero voltage during a high-voltage period within the first stage of the first scanning electrode.

The invention discloses a pulse electrochemical reactor control method for treating complex water in an oil and gas field, which is applied to a control system comprising a pulse power supply, a pulse electrochemical reactor and a controller, an electrode system is arranged in the pulse electrochemical reactor, and during the operation period of the pulse electrochemical reactor, the pulse electrochemical reactor is connected with the controller. Periodically interrupting the treatment pulse applied to the electrode system, controlling the pulse power supply to apply a preset alternating current disturbance signal to the electrode system, and collecting an electrochemical response signal fed back by the electrode system; based on the parameters of the alternating current disturbance signal and the parameters of the electrochemical response signal. By monitoring the electrochemical state of an electrode interface in real time and dynamically adjusting pulse parameters and adaptive water quality changes, efficient and stable operation of the reactor is realized; the technical problems of dynamic response lag, insufficient control precision and shortened equipment service life caused by static parameter setting in a pulse electrochemical reactor control method in the prior art are effectively solved.

The invention discloses a current sensing measurement device and method, a storage medium and electronic equipment, and the device comprises an AC detection module which is used for sensing an AC current and outputting an AC current analog signal; the direct-current compensation module is used for acquiring magnetic induction intensity generated by a direct-current component of the detected current and outputting a differential voltage analog signal; the compensation module is used for outputting compensation current which is equal to the direct-current component in size but opposite to the direct-current component in direction based on the compensation control signal output by the signal processing module so as to offset direct-current magnetic flux generated by the direct-current component; and the signal processing module is used for calculating a direct current component, a compensation current and an alternating current based on the alternating current analog signal and the differential voltage analog signal, and outputting the compensation control signal based on the direct current component. According to the invention, direct current interference can be effectively suppressed, air gap nonlinear errors can be compensated, influences caused by environmental changes and equipment aging can be adapted, high precision and high reliability of a measurement system can be maintained during long-term operation, and the requirement of high-precision field calibration can be met.

The invention discloses an AC arc fault weak signal detection method, device and equipment and a medium, and the method comprises the steps: obtaining a bus current signal of a low-voltage power distribution system, carrying out the amplitude standardization preprocessing of the bus current signal, and generating a normalized signal; performing time-frequency domain feature fusion extraction on the normalized signal to generate a comprehensive feature vector; performing fault diagnosis on the comprehensive feature vector by adopting a nested sliding window mechanism to generate a fault diagnosis mark; and based on the comprehensive feature vector and the fault diagnosis mark, utilizing a pre-trained classification model to generate an arc fault classification result. According to the method, through the synergistic effect of signal noise reduction, feature fusion, real-time diagnosis and intelligent classification, the detection sensitivity is improved to reliable identification in a low signal-to-noise ratio-10dB scene, the real-time performance meets the UL1699 standard requirement, and the core problem that weak alternating current arc fault detection sensitivity and real-time performance are insufficient is solved.

The invention discloses an optical flux-inductance-energy integrated system and a transmitted waveform design method, and the method comprises the steps: carrying out the MLS modulation and OFDM modulation of an input original signal, obtaining an MLS waveform and an OFDM waveform, carrying out the amplitude distribution of the two waveforms, and combining the two waveforms according to a time sequence to form an MLS-OFDM AC signal; after the alternating current signal is subjected to digital-to-analog conversion, outputting the alternating current signal according to a set driving peak-to-peak value voltage, superposing a direct current component in the alternating current signal so as to carry out alternating current and direct current amplitude distribution, and outputting an analog electric signal; the transmitter converts analog electric signals into optical signals, and the optical signals are simultaneously connected with the information decoding module, the sensing processing module and the energy collecting module. According to the hybrid MLS-OFDM waveform design scheme combining alternating-current amplitude distribution and alternating-current and direct-current amplitude distribution, flexible balance among communication, perception and energy collection performance in an optical flux-inductance-energy integrated system is achieved, the complexity of the system can be reduced, and the system is made to be lighter and more compact.

A converter station AC filter group circuit breaker abnormal arcing modeling analysis method comprises the following steps: firstly, carrying out time mark alignment, amplitude calibration and filtering de-noising on wave recording signals such as AC bus voltage and filter branch current to obtain high-quality input data; then, combining a primary wiring diagram, enabling an alternating current system to be equivalent to an ideal power supply and series impedance, enabling circuit breaker arcing to be equivalent to arc resistance changing along with time, and constructing an equivalent circuit model comprising the power supply, the impedance, a capacitor, an electric reactor and dynamic arc resistance; establishing a state space equation according to a voltage and current constraint relation, and performing time domain solution by adopting a two-step two-order or three-order diagonal implicit Runge-Kutta method to obtain voltage and current responses of the whole process of the fault; on this basis, the arc resistance change is inversed according to the ratio of arc voltage to current, the current zero passage is identified through the resistance symbol change at adjacent moments, and the zero passage section is smoothed; and finally, the inversion result is verified again by means of the simplified equivalent model.

The invention relates to the technical field of magnetic shielding, and discloses a self-adaptive active adjustment type magnetic shielding device demagnetization circuit and device, and a control acquisition system, which are used for comparing a residual magnetism state with a preset expected value and generating a control instruction; the energy output identification system is used for outputting an alternating current degaussing signal according to the control instruction to perform degaussing, outputting an excitation pulse signal to perform residual magnetism detection, identifying a zero crossing point of the alternating current degaussing signal and realizing mode switching of degaussing and residual magnetism detection; and the magnetic shielding device is used for demagnetizing under the action of the alternating current demagnetizing signal and feeding back the residual magnetism state of the preset feature point under the action of the excitation pulse signal. The demagnetization is interrupted at the preset feature points in the demagnetization process, the real-time residual magnetism state is collected, and the demagnetization parameter at the next moment is adjusted after the real-time residual magnetism state is compared with the preset residual magnetism expected value, so that the problem of low efficiency due to the fact that the demagnetization parameter needs to be reset after the process is finished is solved, and the demagnetization efficiency and accuracy are greatly improved.

The embodiment of the invention provides an uninterruptible power supply, a control method of the uninterruptible power supply, related equipment and a system, and relates to the technical field of electric power. Comprising a bypass switch and a DC / AC inverter, and the bypass switch is used for responding to the first control signal to be switched on, so that an alternating current power supply provides active power for a load through the bypass switch; the DC / AC inverter is in an inversion state in response to the second control signal, obtains energy from the DC energy storage equipment, and provides active power of the first set power for the load, so that the active power provided by the AC power supply for the load is smaller than the second set power. According to the uninterruptible power supply provided by the scheme, a rectifier part in a traditional uninterruptible power supply framework is omitted, only the inverter and the static bypass are included, the size of the uninterruptible power supply is reduced, and the equipment cost is reduced. Meanwhile, the direct-current energy storage equipment and the alternating-current power supply simultaneously provide active power for the load after passing through the DC / AC inverter, and peak load shifting of the power of the power grid side is achieved.

The invention relates to a DRU-MMC receiving end high-frequency oscillation suppression method and device. The method comprises the following steps: detecting an alternating current system side impedance and detecting whether an alternating current system side voltage has an oscillation trend or not; if it is judged that oscillation occurs, a reverse damping voltage needed to be output theoretically is calculated according to the alternating current system side impedance and serves as a voltage outer ring instruction value; tracking the generated voltage outer loop instruction value and outputting a modulation signal; driving pulses of all bridge arms of the power electronic energy converter are generated according to the modulation signals, so that the series converter is controlled to output active damping to counteract damping on the alternating current system side; according to the detected alternating current system side voltage, the positive sequence voltage phase and the angular frequency of the alternating current system side grid connection point are extracted, the positive sequence voltage phase is used for modulating module phase input, and the angular frequency is used for calculating the reverse damping voltage needed to be output theoretically. Impedance remodeling can be carried out according to the possible oscillation frequency, the positive damping characteristic is presented, and therefore the good oscillation suppression effect is achieved.

The invention belongs to the technical field of resonance stability of a power system, and discloses a high-voltage reactance configuration method for improving resonance stability of the power system, which solves the precision defect caused by neglecting voltage fluctuation in traditional modeling by establishing a fan and static var generator precise admittance model considering DC voltage fluctuation. The dq admittance model of the alternating current system is obtained according to the nodes, connected to the alternating current system, of the fan and the static var generator, general calculation of dq admittance of the multi-node alternating current system is achieved, the limitation that only single-node modeling is supported in a traditional method is broken through, the complex stability problem is quantized into an optimizable amplitude margin index, and the stability of the system is improved. A clear basis is provided for resonance stability analysis, high reactance configuration is expanded from traditional reactive compensation to resonance stability active optimization, and the resonance stability design efficiency of the new energy grid-connected system is remarkably improved.

A control method for suppressing an overvoltage of the receiving end hybrid modular multilevel converter with full-bridge submodules and half-bridge submodules (F / HMMC) under the fault at the receiving-end alternating-current (AC) system of the hybrid high-voltage direct-current (HVDC) transmission system. After a short-circuit fault occurs in a receiving-end AC) system of the hybrid HVDC transmission system, an AC voltage drop is generated, and the effective voltage of the receiving-end AC bus at the current time is measured. Because the hybrid modular multilevel converter (MMC) is capable of actively decreasing the DC voltage for operation, on a premise of ensuring that its output current is always within a rated current range, a control manner of setting the reference DC voltage and making the reference DC voltage not greater than the effective voltage of the AC bus enables receiving end power to be sent out, thereby suppressing an overvoltage of the receiving-end F / HMMC.

The application belongs to the technical field of high-voltage electrical test and detection, and relates to a disc-type insulator alternating current withstand voltage multi-channel leakage current detection method and system. The method comprises the following steps: setting a parameter set comprising a withstand voltage, a frequency, a voltage raising and stabilizing strategy, sampling parameters, a judgment threshold and a consistency threshold, and generating a version identifier; constructing equipotential boundaries and voltage grading electrodes, and organizing a high-voltage end of a to-be-detected insulator, an independent measurement loop and a common ground reference point; synchronously sampling each loop during voltage raising and stabilizing to obtain a multi-channel sequence; filtering and windowing the sequence to obtain an effective value and a stability index; compensating and calculating a consistency index; combining the threshold, a ground state and a communication state to output a judgment and an event marker, triggering voltage reduction or disconnection, and structuring evidence. The technical scheme of the application is suitable for batch detection of alternating current withstand voltage, and can realize judgment robustness and channel consistency control.

Examples described herein provide a circuit that includes a power electronics converter disposed in a vehicle, the power electronics converter to receive alternating current (AC) electrical power from an AC grid source and to provide AC electrical power to an AC load external to the vehicle. The power electronics converter includes an AC-AC converter that includes a rectifier and an inverter, the rectifier being electrically connected to the inverter by a direct current (DC) link. The circuit further includes an on-board charging module electrically connected to the power electronics converter and a battery disposed in the vehicle. The power electronics converter provides vehicle-to-load functionality by providing, to the AC load, AC electric power as an output of at least one of a 120 Vac output or a 240 Vac output.

The invention discloses a method for constructing a correlation mathematical model of time-phased overcurrent capability and electric-thermal limit parameters of a power device of a high-voltage direct-hanging network-constructing energy storage system. Based on the short-time overload capacity requirement of the energy storage system, obtaining a selection range of an alternating current operation point; the alternating current operation point is selected in the range; calculating current flowing through a power device in a converter valve bridge arm of a direct-hanging converter of the energy storage system; calculating the junction temperature of the power device under the alternating current operation point; checking whether the current flowing through the power device and the junction temperature meet an electric-thermal limit constraint condition or not; and classifying the alternating current operation points according to the short-time overload capacity requirement, and further obtaining the active and reactive current safe operation range of the high-voltage direct-hanging grid-constructing type energy storage system.

The invention relates to a high-precision temperature detection system based on an alternating-current impedance bridge. The high-precision temperature detection system comprises a double-resistance bridge circuit, a lock-in amplifier and a differential circuit, the double-resistor bridge circuit comprises a resistive temperature sensor and a standard resistor which are connected in series, and the phase-locked amplifier is a digital phase-locked amplifier realized based on an FPGA (Field Programmable Gate Array). Wherein the initial potential of a first voltage measurement end arranged at the midpoint of the double-resistor bridge circuit is zero by adjusting the two excitation signals which are loaded to the double-resistor bridge circuit and have the same frequency and opposite phases before temperature measurement; in the temperature measuring process, the lock-in amplifier detects the potential of the first voltage measuring end and the voltage at the two ends of the standard resistor through the differential circuit, then the resistance value of the resistance-type temperature sensor is calculated by combining the resistance value of the standard resistor, and then the temperature of the resistance-type temperature sensor is reduced. According to the invention, the anti-interference capability can be improved, and the measurement precision of 0.1 mK level can be reached near 273K.

The invention relates to a low-noise high-precision pressure measuring circuit which comprises a bridge type sensor, an alternating-current excitation signal source, a phase-sensitive detector, a low-pass filter, a reference signal source and a signal conditioning amplifier. The alternating current excitation signal source modulates a differential voltage signal generated by the bridge type sensor to a high-frequency alternating current excitation signal generated by the alternating current excitation signal source to obtain a high-frequency pressure signal; the high-frequency pressure signal is amplified by the signal conditioning amplifier to form a modulated signal; the phase-sensitive detector performs frequency mixing on the modulated signal and a reference signal generated by a reference signal source to obtain a frequency mixing signal; the frequency mixing signal is filtered by a low-pass filter to form a direct-current voltage signal for pressure measurement; the reference signal generated by the reference signal source and the high-frequency AC excitation signal generated by the AC excitation signal source have the same frequency. According to the circuit, signals are modulated to a high-frequency area with low noise energy to be processed by adopting alternating-current excitation and coherent detection technologies, the signals and noise are effectively separated, and extremely high measurement resolution and precision are achieved.

The invention discloses a flexible direct-current power transmission system and a fault ride-through method and system thereof. The flexible direct-current power transmission system comprises a main control module, and a new energy sending-out system, an alternating-current energy consumption device, a sending-end converter, a direct-current circuit breaker, a receiving-end converter and a receiving-end alternating-current power grid which are connected in sequence, the direct current circuit breaker is deployed on a direct current power transmission line between the sending end converter and the receiving end converter, and the receiving end converter is a modular multi-level converter formed by cascading a plurality of half-bridge sub-modules with damping branches; the main control module is in communication connection with the half-bridge sub-modules, the direct-current circuit breaker and the alternating-current energy consumption device and used for controlling the damping branches of the half-bridge sub-modules in the running state, the direct-current circuit breaker and the alternating-current energy consumption device to act when a direct-current fault occurs so as to restrain direct current and adjust direct-current voltage to be within a set voltage range. Therefore, no-locking fault ride-through is completed. According to the invention, high-reliability and low-cost DC fault ride-through can be realized.

The invention relates to the technical field of power transmission systems, and discloses a direct-current power transmission system commutation failure suppression method, system and device and a medium. The method is applied to a direct current transmission system equipped with VDCOL control, and comprises the following steps: measuring a rectification side direct current value, and obtaining a rectification side direct current change rate based on the rectification side direct current value; determining a receiving end AC system operation state based on the rectification side DC current change rate; when the operation state of the receiving end alternating current system is an unsteady state, an inverse compensation voltage is obtained based on the direct current change rate of the rectification side, and the inverse compensation voltage is configured to be a regulating variable of dynamic compensation VDCOL control input; and performing dynamic correction on the rectification side current instruction based on the back compensation voltage to obtain a current limiting instruction, and suppressing inversion side commutation failure according to the current limiting instruction. According to the invention, a complete control link from current change rate detection to commutation failure suppression is constructed, and the operation stability and reliability of the DC power transmission system under complex working conditions are improved.

The invention discloses a steel rail stress measuring system based on electromagnetic ultrasonic orthogonal transverse waves. The steel rail stress measuring system comprises an electromagnetic ultrasonic probe and a signal processing unit, the electromagnetic ultrasonic probe is configured to be an orthogonal coil group with orthogonal axes, the electromagnetic ultrasonic probe generates eddy current under the excitation of alternating current and generates a first transverse wave and a second transverse wave on the steel rail, the propagation directions of the first transverse wave and the second transverse wave are both vertically downward from the center of a rail head of the steel rail, the vibration direction of the first transverse wave is the length direction of the steel rail, and the vibration direction of the second transverse wave is the length direction of the steel rail; the vibration direction of the second transverse wave is the width direction of the steel rail head, and the vibration direction of the first transverse wave and the vibration direction of the second transverse wave are perpendicular to each other to form an orthogonal relation; and the signal processing unit is used for synchronously receiving echo signals of the first transverse wave and the second transverse wave, calculating a propagation time difference between the first transverse wave in the length vibration direction and the second transverse wave in the width vibration direction, and evaluating the axial stress of the steel rail according to the propagation time difference between the first transverse wave and the second transverse wave.

The invention provides a voltage stabilizer based on voltage conversion, a control method and a storage medium, and the voltage stabilizer comprises a PFC chopping boost circuit which receives an input alternating current and a boost duty ratio, carries out the chopping boost of the input alternating current based on the boost duty ratio, and outputs a high-voltage chopping alternating current signal; the positive and negative half-cycle filter circuit is connected with the PFC chopping booster circuit and is used for rectifying and filtering the high-voltage chopping alternating-current signal to obtain a positive voltage-stabilizing chopping alternating-current signal and a negative voltage-stabilizing chopping alternating-current signal; the positive and negative half-cycle voltage reduction and stabilization circuit is connected with the positive and negative half-cycle filter circuit, receives the voltage reduction duty ratio, and performs voltage reduction and stabilization on the positive voltage stabilization chopping alternating current signal and the negative voltage stabilization chopping alternating current signal based on the voltage reduction duty ratio to obtain a preset actual positive electric signal and a preset actual negative electric signal; and the output voltage merging circuit is connected with the positive and negative half-cycle voltage reducing and stabilizing circuit, and integrates the preset actual positive electric signal and the preset actual negative electric signal to obtain a voltage stabilizing electric signal. According to the invention, the voltage fluctuation is quickly responded at low cost.

The invention provides a neutral-point potential control method and system for a three-level converter, and relates to the technical field of intelligent control, positive bus voltage and negative bus voltage are sampled, a voltage deviation value is calculated, an additional control quantity is generated according to the voltage deviation value and a symbol of alternating current, and the additional control quantity is obtained through a symbol function and proportional control processing; performing amplitude limiting processing on the additional control quantity to obtain an amplitude-limited additional control quantity; superposing the amplitude-limited additional control quantity on the positive modulation wave, negating the amplitude-limited additional control quantity, and superposing the negated amplitude-limited additional control quantity on the negative modulation wave to obtain a final positive modulation wave and a final negative modulation wave; comparing the final positive modulation wave and the final negative modulation wave with a carrier wave, and generating a driving signal of the power device; and the on-off of the switching device is controlled according to the driving signal, so that a corresponding level is output to realize neutral-point potential balance. According to the invention, neutral-point voltage low-frequency fluctuation and direct-current offset suppression can be realized at the same time.

The invention provides a digital non-contact alternating-current voltage sensor and a voltage measuring method, the sensor comprises an open-type alternating-current voltage probe, a sensing assembly based on the capacitive voltage dividing principle in the probe converts high voltage on a wire into a first voltage analog signal, and an external grounding shielding layer provides anti-interference protection. Signals output by the probe are sent to the signal acquisition module, a signal conditioning circuit in the signal acquisition module firstly filters, blocks and amplifies the signals, and second voltage analog signals easier to process are generated. And then, the main control unit integrated with an analog-to-digital converter converts the signal into a digital sampling value, and finally, the communication unit outputs a measurement result in a digital signal form. According to the sensor, through non-contact measurement and full-digital processing, safe and convenient alternating current high voltage detection is realized, and stable and anti-interference digital signals can be output.

An alternating-current electromagnetic field stress measurement system, comprising: an excitation signal generation module, an alternating-current electromagnetic field stress measurement stress probe, a signal amplification circuit, an A / D conversion circuit and a processor, wherein the excitation signal generation module is used for loading a sinusoidal alternating-current signal to an excitation coil of the alternating-current electromagnetic field stress measurement stress probe, such that a periodically changing electric field is generated on a measured magnetic object; the alternating-current electromagnetic field stress measurement stress probe is used for sequentially routing a stress characterization signal, which is detected from the measured magnetic object, through the signal amplification circuit and the A / D conversion circuit, and then sending the stress characterization signal to the processor; and the processor is used for processing the received stress characterization signal by using an optimized J-A model in which an implicit equation originally characterizing a change in the magnetization intensity or magnetic induction intensity along with stress is made explicit, so as to calculate the stress of the measured magnetic object. The alternating-current electromagnetic field stress measurement system can monitor the stress increase trend in real time, and notice potential dangers in time. Further comprised is an alternating-current electromagnetic field stress measurement method and a computer program for executing the alternating-current electromagnetic field stress measurement method.