527 results about "Current amplitude" patented technology

The invention discloses a fault ride-through hierarchical control method for a network-constructed converter, and the method comprises the steps: introducing a virtual resistor formed by fault current negative feedback into the voltage and current inner loop control of the network-constructed converter based on VSG control through a current inner loop dynamic amplitude limiting control layer after the converter enters a fault ride-through state, the size of the virtual resistor is adjusted in real time along with the amplitude of the fault current so as to carry out dynamic current limiting control on the virtual resistor; and the power outer loop dynamic compensation control layer dynamically adjusts an active power instruction value and a reactive power instruction value of the network construction type converter based on VSG control during the fault ride-through period according to the voltage drop degree of the power grid after the converter enters the fault ride-through state. And respectively performing active-frequency control and reactive-voltage control based on the active power instruction value and the reactive power instruction value. In addition, the method also comprises a state coupling and parameter self-adaption module. According to the method, the GFM converter can have better dynamic performance in the fault recovery stage.

The invention relates to the technical field of ground resistance detection, in particular to a single-core cable ground resistance detection method capable of resisting strong power frequency interference. High-frequency signals are injected in a non-contact mode through a coupling type capacitor clamp, background voltage and current signals are collected firstly, and injection frequency far away from power frequency and harmonic waves is selected through Fourier analysis; cancelling background noise by adopting a normalized least mean square adaptive filter to generate an enhanced signal; the signal is down-converted to a base band through digital quadrature demodulation, a Kalman filter estimates the amplitude and the phase in real time, and the state and noise parameters are periodically calibrated through a compressed sensing algorithm; and finally, loop impedance is calculated according to the voltage and current amplitudes and the phase difference to obtain grounding resistance. The method has the advantages of being non-contact, high in safety, strong in anti-interference capability, high in measurement precision and the like, and is suitable for monitoring the grounding state of the cable in a complex electromagnetic environment.

The invention provides a fault ride-through control method and a fault ride-through control system for a grid-forming converter, which are characterized in that the current of the grid-forming converter under an asymmetric fault is controlled by adopting a negative-sequence current reference generation strategy aiming at an inner ring of a controller, and negative-sequence reactive current is injected into a power grid; adopting a partial sequence current amplitude limiting strategy to control the maximum phase current amplitude of the injected asymmetric current not to exceed an amplitude limiting value; controlling the boundary of an active reference value by adopting an active reference value amplitude limiting strategy for an active synchronization ring; a synchronous damping link is adopted to enhance damping in power angle swing; for a reactive voltage loop, a reactive voltage variable coefficient control strategy is adopted to control the output of the maximum reactive current; and an internal potential locking strategy is adopted to suppress overvoltage. According to the invention, negative-sequence reactive power is provided, and overcurrent of each phase is avoided; the power angle characteristic is improved, and the transient stability is improved; stable transient voltage support is provided in a current output capability range; and after the fault is recovered, the voltage of the converter grid-connected point is smoothly recovered.

A low voltage ride through control method for a grid-forming inverter based on dynamic internal potential adjustment comprises the following steps: detecting a voltage per unit value of a grid-connected point in real time, and comparing the voltage per unit value with a threshold value to judge a voltage drop event and trigger low voltage ride through control; dynamically calculating active and reactive power reference values through a reactive compensation equation and an active current limiting equation according to the voltage amplitude and the power reference value before falling during the ride-through period; inputting the active reference value into a virtual rotor motion equation to generate a reference phase, and outputting a phase reference signal in combination with a dual-mode phase compensation controller; superposing the reactive reference value with the reference voltage through a reactive voltage regulating ring to generate a voltage amplitude reference signal; synthesizing an internal potential according to the phase and the amplitude reference signal, and obtaining an inductive current reference value through virtual impedance control and current amplitude limiting; and finally, a driving signal is generated through the current inner loop controller and the modulation module. According to the invention, overcurrent can be effectively inhibited, rapid reactive power support is provided, and synchronous stability and smooth transition in a fault period and a recovery process are ensured.

The invention provides a low-voltage ride-through control method for a grid-forming type grid-connected converter based on reactive power synchronization, and belongs to the technical field of converter low-voltage ride-through control. When the voltage of a power grid drops, a current amplitude limiting module in the power grid sends a control switching signal to trigger low-voltage ride-through control, and the low-voltage ride-through control is switched to a reactive power synchronization mode; a reactive power synchronous control gain KQs is calculated according to an inner loop gain coefficient Kcp, a current amplitude limiting value, a power grid voltage Vg and a grid side inductance Lgi, a virtual power angle reference value is generated by combining a set reactive power direct current component reference value QN, so that a power angle delta is stabilized in a range close to a normal working point, and a control effect is verified by comparing with a traditional method. According to the method, the system can quickly recover to a normal working state regardless of the duration of the fault and the severity of the fault, meanwhile, the system can effectively work under different power grid fault levels, and the robustness of the system is further enhanced.

The invention relates to the technical field of network construction type converter control, in particular to a network construction type converter fault ride-through method and system based on dynamic virtual resistance control, and the method comprises the steps: adding a control link based on virtual impedance in a network construction type converter control system; detecting the actual value of the power grid voltage, and judging whether the power grid voltage drops or not; detecting the current amplitude output by the grid-forming converter in real time, and judging whether the current amplitude exceeds a set value or not; if one of the two conditions is met, a virtual impedance control link is started: stage-type current limiting control is performed on the virtual resistor, and the size of the virtual resistor provided by the network-forming converter to the power system is adjusted in real time along with the amplitude of the fault current; and when the power grid voltage recovers and the current amplitude is smaller than the set value, the virtual resistor staged current-limiting control exits. According to the invention, the amplitude limiting of the fault current in the fault ride-through of the network-constructed converter can be realized, so that the fault ride-through capability and transient stability of the network-constructed converter are improved.

The invention relates to the technical field of electronic component testing for investigating or analyzing internal microstructures and physical properties of materials by utilizing an electrical means, and discloses an online testing and analyzing method for physical properties of electronic component materials, which comprises the following steps of: constructing a composite excitation signal formed by linearly superposing a main carrier voltage and a perturbation wave voltage; applying the signal to a to-be-tested electronic component and acquiring response current; and extracting an intermodulation current amplitude at an intermodulation frequency point in the frequency spectrum of which the linear response interval is excluded, calculating a nonlinear response coefficient of the material in combination with the excitation amplitude, and comparing the nonlinear response coefficient with a preset degradation threshold so as to judge whether the nonlinear response coefficient is qualified or not. By extracting intermodulation components which cannot be generated by linear contact resistance, physical isolation of external contact noise in a frequency domain is realized, and the problem that contact resistance fluctuation and material intrinsic aging cannot be distinguished in a traditional linear impedance test is solved.

The invention relates to the technical field of motor state monitoring, in particular to a motor state monitoring method and system based on data driving, and the method comprises the following steps: synchronously collecting a motor voltage signal amplitude time domain sample and a motor current signal amplitude time domain sample for a power frequency period in a motor operation state; and calculating an instantaneous phase difference between each corresponding sample point to obtain an instantaneous phase difference original data stream of the motor. The method comprises the following steps: synchronously acquiring voltage and current amplitudes during operation of a motor in real time, and calculating an instantaneous phase difference between the two amplitudes to obtain an electromagnetic state original data stream; further executing high-pass filtering and performing spectral analysis to filter interference signals and low-frequency trend influences, and improving the recognition precision and robustness of instantaneous phase difference jitter features; meanwhile, voltage pulses are actively injected into the winding, echo signals are collected, and rapid capturing and positioning of the abnormal state of the winding are achieved through propagation time delay calculation and impedance characteristic construction.

The invention relates to the technical field of power distribution network fault early warning, and discloses an early warning system and method for a power distribution network ground fault. The data acquisition module of the system acquires multi-mode monitoring data such as zero-sequence current waveform, grounding wire current amplitude phase, insulator leakage current and environment temperature and humidity of the power distribution network in real time, and comprehensively reflects the operation state of the power distribution network. And the feature fusion module performs spatial-temporal feature compensation on the multi-modal monitoring data to generate a fault feature tensor, so that the insulation degradation evolution period of the topological node of the power distribution network is determined, and the insulation state change is accurately evaluated. And the risk deduction module analyzes a dynamic communication path of the topological structure of the power distribution network, performs fault conduction modeling, determines a ground fault risk situation level in combination with multi-modal monitoring data, and comprehensively considers fault conduction characteristics and operation conditions. The early warning decision module generates a dynamic early warning strategy according to the insulation degradation evolution period and the risk situation level, and the early warning mode is flexibly adjusted.

The invention discloses a self-adaptive charging and discharging coordination control method and system for an energy storage battery, and relates to the technical field of charging and discharging control of the energy storage battery. The method comprises the following steps: correcting a maximum allowable current based on a real-time collected SOC and a preset battery low charge threshold, a battery high charge threshold, a reference coefficient, a first attenuation coefficient and a second attenuation coefficient to obtain an inner loop current amplitude limit; judging whether the current system reaches current saturation or voltage saturation, and marking a corresponding saturation mark; calculating a saturation difference value and a saturation direction angle based on the current value controlled and output by the inner ring and the current value actually output by the inner ring; according to the saturation mark, the saturation difference value and the inner loop current amplitude limit are used for correcting the preset outer layer reference power, the corrected reference power is obtained, the integration gain in the preset integration link is corrected, and the saturation state is relieved; stability and reliability of charging and discharging control of the energy storage system are guaranteed, power control precision is improved, service life of equipment is prolonged, and energy conversion efficiency is improved.

The invention provides a power distribution network fault section rapid calibration method based on a feeder terminal. According to the method, power distribution network line electrical quantity and distributed power supply output information are collected in real time through a feeder terminal and preprocessed, then fault transient signals are processed through complete set empirical mode decomposition of mean value self-adaptive noise, and intrinsic mode components are obtained to judge fault types. Thirdly, fault section preliminary positioning is carried out, and an approximate area is determined according to a positive sequence voltage vector for a symmetric short-circuit fault, a negative sequence voltage vector for an asymmetric short-circuit fault and a zero sequence current amplitude for a single-phase earth fault; then accurate calibration is carried out, a single-phase earth fault is judged through a filter and correlation coefficients, and short circuit and broken line faults are calibrated through a model or an intelligent algorithm in combination with line topology and electrical parameters. And finally, establishing a target function containing a penalty term, converting the target function into a Markov decision process, solving through an approximate dynamic programming algorithm, realizing rapid and accurate calibration of a fault section, and improving the power supply reliability of the power distribution network.

The invention discloses a low-voltage distribution box temperature rise abnormity identification method based on an improved fuzzy clustering algorithm. The method comprises the following steps: S1, generating a temperature-current synchronous acquisition data set according to a time sequence; s2, constructing a load-temperature difference weight matrix in combination with the current current amplitude; s3, obtaining a current membership matrix and a cluster center set; s4, calculating the membership slip amount of each measuring point according to the current membership matrix and the membership matrix at the previous moment, and generating a temperature rise trend state sequence; s5, judging whether the temperature rise trend state sequence has a measuring point which continuously slides from the normal cluster to the risk cluster or not; if yes, corresponding cluster centers in the corresponding cluster center sets are extracted and mapped to the physical coordinates according to the measuring point index table, and positioning information containing the measuring point numbers, the types of the electrical parts and the risk levels is generated. According to the invention, the fault positioning accuracy and the operation and maintenance efficiency are greatly improved.

The invention relates to the technical field of electromechanical hydraulic systems, and particularly discloses a low-temperature cold start control method based on high-frequency injection, which comprises the following steps: analyzing a motor state, and carrying out observation and feed-forward compensation on disturbance caused by the motor state to a load torque and a viscosity coefficient through a sliding mode observer algorithm; according to the motor state, obtaining a state equation, constructing an extended sliding mode observer equation, deriving to obtain an observer error equation, and observing the load torque; analyzing the obtained load torque, wherein the motor load torque reflects the oil viscosity; high-frequency current injection, injection frequency control, skin effect enhancement and current amplitude control are carried out in a low-temperature state according to an oil viscosity result, copper loss and a high-frequency magnetic field eddy current effect are used for assisting heat generation, and according to a final oil viscosity result, when electromagnetic heat generation viscosity is reduced and a load is reduced, an injection voltage amplitude is gradually reduced. And after a normal starting condition is reached, switching to normal id = 0 control.

The invention relates to the technical field of state monitoring, in particular to a state monitoring method and system based on a power grid intelligent Internet of Things gateway device, and the method comprises the following steps: based on the Internet of Things gateway device, collecting and analyzing multiple types of sensor signals, carrying out the unified arrangement to form a multi-parameter cooperative monitoring sequence, and comparing the changes of current and voltage signals; and extracting a synchronous response ratio feature group, calculating a thermoelectric trend consistency index in combination with the temperature change trend and the current amplitude, screening an interference level section, and judging abnormal linkage. According to the method, cross-parameter trend extraction, collaborative response, difference comparison and section identification are realized, correlation characteristics of multi-source signals in a continuous time period can be converted into identification basis, an abnormal forming process, a response link and state evolution are discriminated by combined characteristics, and abnormal section, sequence attributes and synchronization factors are jointly applied, so that the accuracy of the multi-source signal identification is improved, and the reliability of the multi-source signal identification is improved. And the identifiability and the classification capability of abnormal events under complex working conditions are improved.

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.

The invention provides a zero-voltage ride-through control method for a self-synchronizing voltage source doubly-fed wind turbine generator, which comprises the following steps that: when the self-synchronizing voltage source doubly-fed wind turbine generator is in a transient state, a grid-side converter adopts vector control, and a rotor-side converter adopts additional virtual impedance and annular current limiting; the transient overcurrent of the grid-side converter and the rotor-side converter can be effectively suppressed, so that the continuous operation capability of the wind turbine generator in the zero-voltage ride-through period can be maintained; meanwhile, by improving the transient capacity and the transient reactive current amplitude of the converter, the transient voltage supporting capacity of the wind turbine generator during the zero voltage ride-through period can be effectively provided; when the self-synchronizing voltage source doubly-fed wind turbine generator set is in a transient state, overvoltage of direct-current bus voltage is limited by a Chopper circuit, active-priority current amplitude limiting control is adopted by a grid-side converter, parameters of a current inner ring PI controller of a rotor-side converter are optimized, energy balance of a direct-current side can be achieved in the zero-voltage ride-through period, and stability of the direct-current bus voltage is maintained.

The invention discloses a fault early warning method and system for an energy storage power station, and relates to the technical field of battery fault measurement. By collecting system side current, energy storage side current, energy storage side voltage and a control mode state word, the phase difference between the energy storage side current and the energy storage side voltage is calculated to judge the battery state; calculating to obtain a suppression operator through a control mode status word and energy storage side current, carrying out damping integral processing through energy storage side voltage to obtain a power angle prediction correction value, and calculating Euclidean distances between equivalent impedances of the battery cells in combination with the suppression operator and the power angle prediction correction value to obtain an impedance dispersion index; the method comprises the following steps: reconstructing an energy storage side current amplitude by using a suppression operator, correcting a phase in combination with a power angle prediction correction value to obtain a compensation function, carrying out compensation calculation on an energy storage side current based on the compensation function to obtain a compensated current, calculating a differential current, and carrying out fault early warning judgment according to the differential current, an impedance dispersion index and an angular frequency deviation correction value. And graded early warning and accurate positioning are realized.

The invention relates to the technical field of power battery charging, in particular to an electric quantity SOC correction method and system for a power battery, and the method comprises the steps: determining a correction demand index at each moment based on the change characteristics of an electric double-layer capacitor and the influence degree of a polarization resistor on the SOC; according to the capacity of the dynamic battery and the temperature change characteristic of each moment, determining a dynamic proportion parameter of each moment by adopting an Arrhenius equation, combining the dynamic proportion parameter with the correction demand index in the correction period of each moment, determining the predicted offset of the SOC of each moment, and determining the SOC after initial correction of each moment; based on the current amplitude of the moment before each moment, the battery standing time of each moment is determined, and the filtering window width is determined by combining the fluctuation condition of the current in the correction period of each moment; and carrying out secondary correction on the SOC after the primary correction in combination with a filtering operation. The invention aims to improve the accuracy of the corrected SOC in a dynamic environment.

The invention discloses an adaptive virtual impedance-based fault current limiting method for a network-forming converter, and belongs to the technical field of converter control. Comprising the following steps: collecting grid-side voltage, converter-side voltage and converter output current; carrying out current amplitude calculation on the grid-side voltage quantity to obtain a current effective value of the port of the converter; judging whether the current effective value of the current transformer port exceeds a current threshold value of the current transformer; and if yes, self-adaptive virtual impedance is introduced to carry out converter fault current limitation. The resistance part of the virtual impedance is used for suppressing surge current at the beginning of a fault; and the reactance part is used for suppressing the effective value of the fault transient current within the current limiting range. In the fault process, the current virtual impedance value is adaptively changed according to the effective value of the current overcurrent, and the virtual impedance can be automatically quitted after the fault end stage. The method is suitable for fault current suppression of the network-forming converter in various control modes, and has good feasibility and practical value.

The invention provides a speed regulation purging control method and system for a steam soot blower, and relates to the technical field of steam soot blower control. Stroke position data of a soot blowing gun barrel and a current signal of a driving motor are obtained and synchronously associated, and the speed regulation purging control method and system for the steam soot blower can be realized on the basis of data collected in a plurality of purging cycles. And identifying current anomalies which appear for multiple times at the same stroke position and have consistent current amplitudes and change forms, and identifying the stroke position as a fixed mechanical resistance position. For each fixed mechanical resistance position, a dynamically adjustable mechanical resistance reference value is determined. In the real-time purging process, according to the mechanical resistance reference value, the actual coking resistance signal value is obtained through separation from the total current value of the driving motor, and therefore the purging parameters of the soot blower are adjusted, the service life of the soot blower nozzle and the boiler heating surface can be remarkably prolonged, the operation cost is reduced, and the energy consumption is reduced. And intelligence and refinement of soot blower control are realized.

The invention relates to a single-loop control method for a static synchronous phase modifier, which belongs to the technical field of power systems, and comprises the following steps of: comparing a maximum voltage difference value in three phases with a preset voltage threshold value to obtain a voltage difference value after amplitude limiting, and obtaining a first virtual reactance by using the voltage difference value after amplitude limiting and a preset current amplitude limiting threshold value; performing proportional integral control on the difference between the maximum current value in the three phases and the current amplitude limiting threshold to obtain a second virtual reactance; virtual impedance is calculated according to the first virtual reactance and the second virtual reactance; the product of the virtual impedance and the current of each phase is used as the current amplitude limiting voltage of the corresponding phase; the modulation wave of the corresponding phase is generated by using the internal potential and the current amplitude limiting voltage of each phase, so that the voltage single-loop control and the fault current amplitude limiting of the static synchronous phase modifier are realized, the broadband oscillation risk and the overcurrent risk of the converter are effectively reduced, and the safety and the reliability of static synchronous phase modifier equipment are improved.

The invention relates to the field of capacitor monitoring, and provides a capacitor quasi-online state monitoring method and system for a wind power converter, and the method comprises the steps: extracting a data slice comprising DC bus voltage, capacitor branch current, housing temperature and output power from a data buffer area; furthermore, output power data is utilized, intelligent screening is carried out through a quasi-steady-state slice trigger, and only effective data with the power average value large enough and the fluctuation small enough are reserved. And for the screened effective data slices, extracting the DC bus voltage and the capacitance branch current, and accurately identifying the voltage, current amplitude and phase information of the main harmonic through fast Fourier transform. Based on the key harmonic data, the complex impedance of the capacitor is calculated, and then the original ESR and capacitance estimation value are calculated. And finally, in combination with the capacitor shell temperature extracted from the same data slice, performing temperature compensation on the original parameters, and outputting a final result capable of truly reflecting the aging state of the capacitor.

The invention discloses a dual three-phase permanent magnet synchronous motor winding open-circuit fault diagnosis method, belongs to the technical field of motor control and fault diagnosis, and aims to solve the problem that a fault continuously damages a motor during the existing dual three-phase permanent magnet synchronous motor open-circuit fault diagnosis period. The method comprises the following steps: mapping six-phase stator current to a torque plane, a harmonic plane and a zero-sequence plane through vector space decoupling transformation; decomposing the current of the torque plane into two independent torque sub-plane currents; monitoring the harmonic current amplitude of the harmonic plane, and when conditions are met, starting a fault diagnosis process: according to the characteristics of the two torque sub-plane currents in a half fundamental wave period, calculating a primary fault flag bit, and judging the type of an open-circuit fault; calculating a secondary fault flag bit, and positioning a single-phase open-circuit fault and a two-phase open-circuit fault; in the diagnosis process, a phase-locked loop based on a second-order generalized integrator is synchronously utilized to update a harmonic current reference value so as to suppress motor torque fluctuation.

The invention provides a barrier gate equipment remote fault intelligent diagnosis system and method, and the method comprises the steps: extracting a motor current amplitude sequence of each complete action period from motor current data of barrier gate equipment, and determining the current deviation characteristics of the barrier gate equipment in a single complete action period according to all motor current amplitude sequences; extracting a vibration effective value sequence of each complete action period from the case vibration data of the barrier gate equipment, and determining vibration impact characteristics of the barrier gate equipment in a single complete action period according to each vibration effective value sequence; and performing combined diagnosis on the current state of the barrier gate equipment through the current deviation characteristic and the vibration impact characteristic, outputting a fault type and a fault confidence coefficient of the barrier gate equipment, and when the fault confidence coefficient exceeds a credible threshold value of the barrier gate equipment, performing remote graded alarm on the barrier gate equipment based on the fault type. Based on the scheme, multi-cycle fusion diagnosis of the multi-source sensing data in the barrier gate equipment can be realized.

The invention belongs to the field of power grid system control, and discloses a power grid system virtual impedance dynamic control method, system and device and a medium. The control method comprises the following steps: judging whether the power grid system breaks down or not by acquiring power characteristics of electronic equipment in the power grid system, including content proportions of voltage harmonics and current harmonics, current amplitude changes and positive and negative sequence voltage amplitudes. When a fault occurs, normal virtual impedance is calculated and combined with response current of harmonic waves to obtain dynamic virtual impedance, and then self-adaptive virtual impedance is comprehensively obtained and switched to the impedance value. According to the method, rapid and accurate dynamic current limiting and reactive power supporting under the complex fault working condition are achieved, the adaptability and stability of power electronic equipment to power grid faults are improved, fault current is effectively restrained, equipment damage is prevented, and meanwhile the transient characteristic and reliability of a system are enhanced.

The invention discloses a rotor initial mechanical angle identification method of a built-in permanent magnet synchronous motor, and relates to the field of motor control. When the motor is offline, a fitting function model corresponding to a three-phase high-frequency response current amplitude and a rotor mechanical angle of the permanent magnet synchronous motor is measured and established in advance; constructing a three-dimensional data table by using the fitting function model; when the motor runs, a high-frequency injection voltage between lines is input, a real-time three-phase high-frequency current response amplitude value is collected, and matching search is carried out on the three-dimensional data table, so that a mechanical angle mapped by an obtained error minimum value is used as an initial mechanical angle of a rotor obtained by matching search; and inputting the initial mechanical angle of the rotor into a control system of the permanent magnet synchronous motor. Thus, when the rotor is static at any mechanical angle, the absolute mechanical angle position of the rotor can be directly and uniquely determined without any pre-positioning operation, and the problems of running blind areas, pre-positioning strokes, reverse rotation risks and vibration noise are effectively solved.

The invention discloses a power distribution network reliability intelligent analysis method and analysis system, particularly relates to the technical field of power system fault detection, and is used for solving the problems of misjudgment and missed judgment caused by fault feature weakening and harmonic interference in a bidirectional power flow scene in an existing method. The method comprises the following steps: firstly, synchronously collecting fundamental wave and harmonic components of nodes of a power distribution network, extracting a current amplitude change rate and a phase offset by adopting time-frequency domain conjoint analysis, and generating dynamic distribution characteristics by combining harmonic energy clustering; identifying high-frequency interference components in a bidirectional power flow mode by quantizing a phase deviation direction and harmonic energy aggregation characteristics; based on a harmonic frequency band coupling effect and a current dynamic association relationship, an adaptive detection threshold function is constructed, and accurate separation of fault features is realized; and finally, combining a real-time fault judgment result with historical repair data to generate a reliability evaluation parameter. And the sensitivity of fault detection and the rationality of reliability evaluation in a complex operation environment are remarkably improved.

The invention discloses a dry-type air-core reactor loss measurement method, device and system, and relates to the technical field of reactor loss factor measurement. The method comprises the following steps: in response to an obtained electrical parameter signal of the dry-type air-core reactor, performing Fourier transform on a voltage signal in the electrical parameter signal, and determining the fundamental wave purity of the dry-type air-core reactor; the electrical parameter signal comprises a voltage signal and a current signal, the voltage signal comprises a voltage amplitude and a voltage phase, and the current signal comprises a current amplitude and a current phase; based on the current amplitude and the phase difference between the voltage phase and the current phase, determining a harmonic judgment value of the dry-type air-core reactor; determining a defect correction coefficient of the dry-type air-core reactor based on the phase difference between the voltage phase and the current phase; and determining the loss factor of the dry-type air-core reactor based on the fundamental wave purity, the harmonic judgment value and the defect correction coefficient of the dry-type air-core reactor. According to the invention, the identification precision of the defects of the dry-type air-core reactor can be improved.

The invention discloses a flyback photovoltaic micro inverter grid-connected control method and system, and the method comprises the steps: sampling photovoltaic output voltage and current, power grid voltage and grid-connected current, and obtaining discrete sampling values; generating an input current reference value of the flyback converter, subtracting the input current reference value from an actual value, and outputting a grid-connected current amplitude through first PI regulation; a grid voltage sampling sequence obtains a phase through a phase-locked loop, and multiplies the phase with an amplitude and a phase sine absolute value to generate a grid-connected current reference value; the difference between the reference value and the grid-connected current is adjusted by a second PI to output a modulation wave, and the modulation wave is compared with a triangular carrier to generate an H-bridge switch tube PWM signal; mPPT control is executed through the flyback converter and a grid-connected current amplitude instruction is generated, and the H-bridge inverter performs current tracking inversion, so that a set of efficient and cooperative two-stage control strategy is formed, high-quality grid connection of photovoltaic energy is realized, and the problems of huge size, shortened service life and reduced reliability of the existing device are solved; and the overall performance and the long-term operation reliability of the photovoltaic micro inverter are obviously improved.

The invention discloses a fault ride-through method, device, equipment and system based on virtual impedance. The method comprises the following steps: in response to a fault ride-through instruction, obtaining real-time voltage and real-time current of a power grid transmission line, virtual internal potential of a first control loop and a fault current amplitude limiting value of an inverter; determining a first reactive power parameter value and a first active power parameter value based on the real-time voltage and the fault current amplitude limiting value; determining a current reference value based on a preset control target coefficient, the first reactive power parameter value, the first active power parameter value and the real-time current; determining positive sequence virtual impedance and negative sequence virtual impedance according to the current reference value and the virtual internal potential; and on the basis of the positive sequence virtual impedance and the negative sequence virtual impedance, the control parameter output by the second control loop is adjusted, according to the embodiment of the invention, the fault ride-through of the grid-forming inverter can be ensured while the current amplitude during the fault ride-through period is not out of limit, and the power supply reliability is improved.