415 results about "Phase displacement" patented technology

The invention relates to the technical field of abnormity early warning, in particular to a transformer load abnormity early warning method and system, and the method comprises the following steps: obtaining an electrical parameter sequence and correcting a phase, constructing a current and power change rate sequence, extracting a load fluctuation trend factor, calculating a disturbance growth rate and judging whether the disturbance growth rate crosses a boundary, and recognizing a power gradient abrupt change feature. And judging whether periodic overlapping exists or not, and outputting a combined abnormity early warning identification sequence. According to the invention, by introducing phase difference and time base offset calculation, constructing a phase-aligned electrical parameter sequence group, and analyzing a periodic rate mean value and an integral quantity, disturbance trend evaluation is realized, a power gradient sequence is used to identify a section mutation interference signal, and a joint anomaly identification mechanism is constructed on two dimensions of a period and a section. The method achieves the composite judgment of the load disturbance trend and sudden change interference, effectively improves the accuracy and response time efficiency of load abnormity early warning, and reduces the recognition error risk caused by hidden fluctuation or local sudden change.

The invention relates to a rectification harmonic suppression control method for a double reverse star transformer. The method comprises the following steps: establishing a rectifier bridge arm phase characteristic parameter table in a control platform, and recording a theoretical conduction phase, winding attribution and waveform synchronization characteristics of a bridge arm; in the operation process of the rectification control unit, the output current of a transformer and the conduction state of a bridge arm are collected, and a rectification operation state data set is generated; and calculating bridge arm conduction phase deviation, and analyzing a corresponding harmonic component to obtain a mapping relation between a bridge arm state and harmonic distribution. And judging whether the current bridge arm configuration meets the phase coverage requirement of the target rectification pulse number or not according to the mapping result, and if not, selecting a standby bridge arm group with a preset phase difference and generating a switching instruction. And the rectification control unit responds to the instruction to lock the current bridge arm conduction path and release the target bridge arm group so as to realize bridge arm resource dynamic reconstruction and rectification performance optimization. Harmonic waves can be effectively suppressed, and the topology adaptability and the output quality of the rectification system are improved.

Disclosed in the present invention are a dual-end monitoring-based partial discharge source localization method and system for high-frequency partial discharge of a high-voltage cable. The method comprises: acquiring operation data and phase velocity test data of a high-voltage cable; when a partial discharge fault occurs in the high-voltage cable, collecting partial discharge signals on two sides of the high-voltage cable by means of sensors on the two sides of the high-voltage cable; performing Fourier transform respectively on the basis of the partial discharge signals on the two sides to obtain amplitude-frequency characteristics of the partial discharge signals, and preprocessing the collected partial discharge signals on the basis of the amplitude-frequency characteristics to optimize and improve a phase difference algorithm; and by incorporating the phase velocity test data of the high-voltage cable, using the improved phase difference algorithm to perform partial discharge source localization on the faulty cable. In the present invention, dual-end monitoring is used to reduce the attenuation of signals caused by long-distance transmission, and synchronization of two sensors is performed using a PTP protocol, effectively reducing errors; and in addition, during monitoring, partial discharge source localization is performed using the improved phase difference algorithm, which is conducive to resisting external interference, and there is no need to determine the time of arrival, greatly improving the positioning accuracy.

The invention relates to the technical field of electric power engineering automation, in particular to a low-voltage equipment power factor automatic adjusting system and method based on end compensation, and the system comprises a load monitoring module, a compensation strategy generation module, an end compensation execution module, a dynamic balance correction module and an effect evaluation module. According to the invention, the sequential relationship between the load fluctuation and the compensation demand can be accurately identified by continuously monitoring the current waveform, the voltage waveform and the phase difference change trend of the low-voltage equipment, and the compensation strategy is dynamically formulated in combination with the response duration and the compensation demand matching rule, so that the compensation response agility and the matching property of the fluctuating load are improved; dynamic scheduling is carried out according to the capacitor switching capacity and the combination relation in compensation execution, switching weight configuration is analyzed and optimized through the power factor change rate before and after compensation and the load synchronization characteristic, the dynamic balance of the compensation process is enhanced, the power factor stability and the load fluctuation matching capacity after compensation are effectively improved, and the compensation efficiency is improved. And the adaptability and continuity of the adjusting effect are enhanced.

The invention relates to the technical field of fault detection, in particular to an electrical equipment fault diagnosis method and system, and the method comprises the following steps: constructing a ratio group of a trigger incremental sequence quantity and a frequency spectrum cluster set based on a partial discharge pulse interval, deducing impedance frequency boundary migration, analyzing a conductor heating and cooling rate difference, and forming thermal response lag information. According to the method, frequency spectrum energy evolution characteristics are extracted through partial discharge pulse interval dynamic behaviors, a frequency migration path is constructed to reflect an impedance boundary fluctuation process, hysteresis effect characteristics are extracted in combination with thermal inertia response differences in a temperature rise stage, and the impedance boundary fluctuation is determined. And analyzing a voltage and current phase fluctuation rule and deducing a change trend of a combined feature, establishing a layer-by-layer progressive judgment logic between multi-stage dynamic coupling features, realizing evolutionary process tracking from local disturbance to a global abnormal state, and improving a fine-grained identification level of an abnormal mechanism in an electrical equipment operation behavior.

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 discloses an AC excitation system rotor initial position on-line identification method and system, and the method comprises the steps: collecting a stator three-phase voltage signal when a stator is no-load, carrying out the Clarke conversion of the signal, obtaining a voltage component under a static coordinate system, and carrying out the low-pass filtering processing; calculating a stator flux linkage based on the stator current and the processed voltage component, and calculating a rotor flux linkage based on the rotor current; the rotor initial position offset is continuously accumulated through closed-loop adjustment by calculating the stator and rotor flux linkage angle and the phase difference until the phase difference approaches zero, and the accumulated rotor initial position offset is output; and combining the mechanical angle output by the encoder with the accumulated rotor initial position offset to obtain a corrected rotor position angle, and updating the corrected rotor position angle to an excitation system. According to the method, the in-phase characteristics of stator and rotor flux linkages are utilized, and the optimally designed low-pass filter is combined, so that the identification precision of the initial position of the rotor is remarkably improved, and the zero offset of the encoder is effectively compensated.

The invention relates to the technical field of motor control, in particular to a harmonic gear motor based on double encoders and a control method thereof, which comprises the following steps: processing linear Hall element signals output by a rotor shaft encoder, including high-frequency noise suppression, direct-current bias calibration, amplitude normalization and phase difference calibration, to obtain accurate orthogonal signals; a double-dq rotating coordinate system phase-locked loop algorithm is adopted, the calibrated orthogonal signals are processed, and the high-precision real-time angle of the motor rotor is obtained through calculation; based on a signal of an output shaft encoder, matching with a preset angle partition of the harmonic reducer, and identifying an absolute position sector where the current output shaft is located; the rotor angle and the sector angle of the output shaft are fused to generate a high-resolution absolute angle of the output shaft; and based on the fused angle information, a magnetic field orientation control algorithm is adopted to drive a motor, and closed-loop control is achieved.

The invention discloses a power distribution network island grid-connected smooth switching control method and system, belongs to the field of power distribution networks, and particularly relates to power distribution system control, and the method comprises the steps: carrying out the feature extraction of a first voltage signal at the island side of a power distribution network and a second voltage signal at the main network side of the power distribution network, and obtaining a quantitative feature value; inputting the quantized characteristic value into an inrush current prediction model to output a closing inrush current prediction range, calculating a width value and a peak amplitude of the prediction range corresponding to each phase time sequence to identify a target phase interval, and evaluating stability contribution of each phase time sequence in the target phase interval to determine a target closing time sequence; and adjusting the output characteristic parameters of the inverter according to the target closing time sequence to obtain an inverter output signal, performing iterative optimization to adjust phase difference compensation, and generating a grid-connected control instruction to control grid-connected smooth switching of the power distribution network island, so that smooth switching during grid connection of the power distribution network island and the main network can be realized, and the stability of the power distribution system is improved.

The invention relates to a light-weight network-based voltage wave crest and wave trough rapid identification method and system, and the method comprises the steps: constructing a multi-dimensional input vector through voltage and load current dual-channel synchronous collection and feature fusion; real-time reasoning is carried out on the voltage wave crest and wave trough probability based on a lightweight neural network, and a high-confidence-coefficient triggering mark signal is generated in combination with dynamic threshold value comparison; mapping the trigger mark into a multi-phase conduction time sequence deviation matrix by using an asymmetric phase deviation algorithm, and dynamically adjusting a phase difference parameter in combination with a load current; and through a complementary PWM control instruction group generation and closed-loop optimization mechanism, ripple cancellation of staggered conduction of the multi-phase switch tubes is realized. The method solves the problem of insufficient ripple suppression caused by high false triggering rate and rigid phase distribution in traditional fixed threshold detection, remarkably improves the voltage stability and dynamic response speed in a sudden change scene from light load to heavy load, and can be widely applied to high-precision power supply systems such as data centers and communication equipment.

The invention provides a thin-wall structural part milling chatter suppression method and device based on main shaft rotating speed parameter adaptive regulation and control, electronic equipment and a storage medium. According to a stability lobe graph, a rotating speed area is divided, and a continuous variable rotating speed dominant area and a discrete variable rotating speed dominant area are determined; if the milling chatter is in a low-speed area, sine continuous variable-speed modulation is adopted, modulation parameters are optimized based on an energy minimization criterion, and a continuous variable-speed curve is generated; if the target is in the high-speed area, calculating a stable target rotating speed according to a phase difference matching condition, and generating a discrete rotating speed sequence through low-pass filtering and saturation constraint processing; and when the stability improvement amplitude is lower than a threshold value, the rotating speed is divided into a discrete variable rotating speed dominant area, and a discrete variable rotating speed strategy is adopted. An additional vibration suppression device or hardware transformation is not needed, and the method has the advantages of being easy and convenient to implement and low in cost and has the remarkable effect in the aspect of improving machining stability and efficiency.

The invention relates to the technical field of power grid switching, and provides a grid-connected and off-grid seamless smooth switching method and device, electronic equipment and a storage medium thereof. The method comprises the following steps: acquiring a power grid phase angle and dq-axis voltage in real time through SRF-PLL phase locking, performing Clarke-Park conversion on VSG output current, and calculating active power and reactive power; based on the power deviation, the virtual inertia and the damping coefficient, dynamic optimization is carried out to obtain self-adaptive inertia and damping; performing secondary voltage compensation by combining the dq-axis voltage amplitude difference and the real-time reactive power to generate excitation voltage; frequency compensation is realized by using a phase difference and a dynamic phase tracking model; a switching instruction is generated through multi-threshold judgment, linear transition is conducted on reference current and reactive power through a transition function during switching, a non-jump current instruction is output, and grid-connected and off-grid seamless switching is achieved by closing PWM. According to the invention, grid-connected and off-grid seamless switching and high-precision voltage frequency control are realized through multi-threshold judgment, soft-closed PWM and the like.

The invention relates to the technical field of fault diagnosis, and discloses a mutual inductor fault diagnosis method and system based on an intelligent algorithm, and a storage medium. The method comprises the following steps: acquiring an output signal of a secondary side of a mutual inductor at a preset sampling frequency, performing de-noising processing on the output signal, and converting the output signal into time sequence data; performing time domain feature extraction on the time sequence data to obtain a first data feature and a second data feature of the target physical quantity, extracting a zero-sequence current component and a zero-sequence voltage component from the time sequence data, and calculating a phase difference between the zero-sequence current and the zero-sequence voltage as a zero-sequence feature; whether the transformer is abnormal or not is judged, if yes, a multi-modal input vector is constructed based on the time domain features, the zero sequence features, the environmental parameters, the temperature parameters and historical fault records, the multi-modal input vector is input into a pre-trained multi-task deep learning model, and the deep learning model outputs a fault diagnosis result. According to the invention, the fault diagnosis precision of the mutual inductor is improved.

The invention discloses a phasor closed optimization control method for secondary harmonic suppression of a direct-current micro-grid, and the method comprises the steps: taking the square of a total harmonic current amplitude as a measurement standard, and searching an optimal harmonic reference phase through a gradient descent method; adjusting the harmonic phase injected into the direct current system by adjusting the phase of the voltage of the alternating current side inverter or changing the harmonic phase generated by the single-phase inverter by adjusting the voltage phase of the single-phase inverter; and an alternating current reference current generating ring is constructed by adopting a bidirectional DC-DC converter in a step-up or step-down mode to ensure that the absorption current and the residual harmonic waves are synchronous in phase, so that the residual harmonic waves are filtered out. According to the invention, under the condition of not damaging the electric energy direct current of the alternating current side, the second harmonic current injected into the direct current micro-grid is reduced, the configuration capacity of the filter is reduced, and meanwhile, the complete absorption of the amplitude and phase difference between the compensation current of the parallel filter and the actual second harmonic current is realized.

The invention belongs to the technical field of magnetic variable measurement, and particularly relates to a power driving compensation method and system for magnetostrictive load characteristic monitoring, and the method comprises the steps: obtaining a reference zero point of magnetic performance evolution in a cold state environment of an electromagnetic system according to the center frequency of the electromagnetic system; calculating a current main frequency impedance module value and a phase difference through an electrical parameter characterization method, and obtaining a thermal drift index reflecting a hysteresis loop distortion degree in combination with a reference zero point; obtaining correction factors of all orders based on the thermal drift index and the average output power at the current moment, and dynamically updating a coefficient vector of the inverse model; and constructing a pre-distortion driving voltage signal capable of counteracting nonlinear interference by using the new coefficient and the ideal guided wave voltage sequence, and inputting the pre-distortion driving voltage signal to a power amplifier to drive the magnetostrictive transducer. According to the invention, the problem of predistortion failure under a variable-temperature working condition in the prior art is solved, and the signal-to-noise ratio of high-power long-distance guided wave detection is remarkably improved.

The invention provides a low-voltage direct-current power distribution network small-current grounding fault identification method based on active injection and phase characteristic analysis and a related device, and the method comprises the steps: responding to a starting criterion of fault detection, and triggering an active signal injection strategy; collecting the positive and negative electrode current of the head end of each feeder line and extracting the zero-mode current of the head end of each feeder line; calculating the total zero mode current of the system; aligning the zero-mode current of each feeder line with the total zero-mode current; extracting instantaneous phases of the zero-mode current of each feeder line and the total zero-mode current by adopting a wavelet transform method; calculating an average phase difference between the zero-mode current of each feeder line and the total zero-mode current; and judging whether the cosine value of the average phase difference is smaller than a set value, and if so, judging that the section to which the corresponding feeder belongs has a fault. According to the invention, the fault features are enhanced by using the active injection detection signal, and the criterion is constructed through zero-mode current processing and phase analysis, so that the fault identification capability is improved under the condition of not adding an additional injection device.

The invention discloses a pre-synchronization control method for a network-building converter based on a virtual synchronous generator, and the method comprises the steps: collecting the three-phase voltage of the output end of the virtual synchronous generator VSG and the three-phase voltage of a power grid side, converting the three-phase voltage into a voltage component in a two-phase static coordinate system through Clark conversion, and extracting a positive-sequence component; calculating a phase difference compensation coefficient based on the positive sequence component; based on the phase difference compensation coefficient, adaptively setting a PI parameter; and calculating and adjusting the amplitude of the internal potential to finish pre-synchronization. In the working process, through self-adaptive PI parameter setting and amplitude accurate judgment, the pre-synchronization time is shortened, the grid-connected impact current is reduced, and the grid-connected success rate of the micro-grid in a weak grid scene is improved.

The invention discloses a withstand voltage test method and device for transformer production and a medium, and belongs to the technical field of transformer tests.The method specifically comprises the steps that firstly, a frequency conversion test power source is connected to the input end of a to-be-tested transformer and connected with a high-precision non-inductive shunt in series, and an environment monitoring unit is started to lock temperature and humidity in real time; the control power supply outputs a standard sine test voltage with a preset frequency; then, a high-frequency broadband acquisition card is used for synchronously obtaining instantaneous waveform data of voltage and total leakage current of the transformer, and analog signals are converted into discrete digital signals; performing second-order difference on the total leakage current signal to position a high-frequency abrupt change point, and reconstructing a smooth waveform through Lagrange interpolation; a current phase difference is calculated by taking a voltage zero crossing point as a phase reference, a complex plane coordinate system is constructed, and resistive and capacitive current components are calculated through waveform amplitude projection; and finally, according to the temperature and the humidity, a correction coefficient is called to normalize the resistive current, and a quality inspection result is output by comparing an insulation safety threshold.

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 relates to the technical field of electric switches, in particular to an electric disconnecting switch interlocked with a pole-mounted circuit breaker and a control method thereof, and the method comprises the steps: obtaining standard coil current data, actual coil current data, main loop three-phase current data, power side voltage data and load side voltage data, and carrying out the preprocessing; determining time division points by using the wave crest and wave trough distribution characteristics so as to divide stage intervals; the health coefficient of the pole-mounted circuit breaker is obtained through stage interval similarity analysis; calculating an electrical isolation coefficient by combining the main loop current level difference and the bilateral voltage amplitude phase difference; and performing hierarchical interlocking control on the electric isolation switch based on the health coefficient and the electrical isolation coefficient. According to the invention, a two-dimensional evaluation system of mechanism health pre-judgment and electrical isolation hard criteria is constructed through multi-source data fusion, and the safety and reliability of distribution network operation are improved through a hierarchical interlocking control strategy.

The invention relates to the technical field of error calibration, in particular to an on-line calibration method and system for errors of a power transformer, and the method comprises the following steps: triggering data collection through setting a voltage and current change rate threshold value, and synchronously obtaining high-frequency waveform data of a primary side and a secondary side of the transformer; and taking the trigger point as a center to intercept a waveform segment of a transient state time period. According to the method, the data acquisition process is triggered by setting the threshold condition of the voltage and current change rate, the abnormal response moment in the operation of the current transformer can be accurately locked, invalid or interference data acquisition is avoided, the data validity is improved, the multi-level wavelet packet decomposition is carried out on the transient waveform, and the accuracy of the data acquisition is improved. The energy ratio and the phase difference between the primary side signal and the secondary side signal are clearly depicted under each frequency band, and the high-resolution identification of the local response transaction is effectively realized by constructing a frequency band response difference sequence and reconstructing the frequency band response difference sequence into a dynamic error feature vector.

The invention discloses a network construction type converter pre-synchronization control method based on Taylor compensation, and the method comprises the steps: collecting the three-phase voltage of an output end of a virtual synchronous generator (VSG) and the three-phase voltage of a power grid side, carrying out the Clark transformation, and extracting a positive sequence voltage component; on the basis of the positive sequence voltage component, calculating a phase difference sine value of the VSG output voltage and the power grid voltage; based on the phase difference sine value, compensating the phase difference sine value through Taylor expansion to obtain a compensated real-time phase difference; and fusing the compensated real-time phase difference into a VSG phase-locked loop-free pre-synchronization control strategy, and driving a PI regulator to dynamically correct the output frequency and phase of the VSG. A phase-locked loop is completely abandoned, and the frequency oscillation risk is eliminated; expanding a phase difference calculation range through third-order Taylor compensation; voltage vector analysis and a dynamic compensation function are fused, phase synchronization is achieved, and grid-connected impact current is reduced.

The invention relates to the technical field of electrical fault detection, in particular to an online fault judgment and automatic detection method for a marine cable, which comprises the following steps of: acquiring ground leakage current and load current in operation, extracting an active component of the leakage current and analyzing the nonlinear correlation between the active component and the load current to realize online early warning of insulation degradation; when the ship is in a working condition of allowing short-time power failure of partial non-critical loops, positioning a fault branch based on a normalization result of the ground capacitance variation before and after the power failure of each branch and the cable length; after power supply is recovered, the fault type is judged by combining the leakage current fundamental wave and phase voltage phase difference and the harmonic distortion rate; during power-off maintenance, high-frequency carrier waves are injected, the position of a fault point is determined according to current attenuation abnormity, correction is carried out by combining temperature and vibration factors, and the detection accuracy and the positioning precision are improved.

The invention discloses a fault determination method and device for a permanent magnet synchronous motor, and a computer program product. The method comprises the steps that in the operation process of the motor, the three-phase current of the motor is acquired according to a preset time period; if the maximum current in the three-phase current exceeds an upper limit current threshold value and the minimum current in the three-phase current is lower than a lower limit current threshold value, acquiring the current rotating speed and torque of the motor; if it is determined that the motor is not in the locked-rotor working condition according to the rotating speed and the torque, determining that the motor has an open-phase fault at present; and under the condition of determining that the motor is in a locked-rotor working condition according to the rotating speed and the torque, if the phase difference between any two phases in the motor does not meet a preset phase loss condition, determining that the motor has a locked-rotor fault at present, and otherwise, determining that the motor has the locked-rotor fault and the phase loss fault at the same time at present. According to the invention, the technical problem that the normal operation of the motor is affected by adopting a wrong protection mechanism due to the fact that misjudgment is easy to occur during motor fault detection in the prior art is solved.

The invention discloses a grid drive short-circuit protection method based on dV / dt detection, which relates to the technical field of power electronics, and comprises the following steps: constructing a unified time frequency reference baseline, executing all-phase mapping on each power device of a parallel system, reconstructing a conduction sequence, and calculating a phase difference between a voltage rising edge and sampling trigger. Generating a time frequency dislocation matrix, and determining a phase dislocation risk window; and executing causal playback in the phase dislocation risk window, extracting transient waveform characteristics of a voltage rising edge, eliminating parasitic pseudo peaks, obtaining an effective response trajectory, generating a sampling phase check anchor point based on the trajectory, and constructing a phase reference baseline. According to the method, a unified time-frequency baseline and a dynamic sampling mechanism are constructed to realize phase synchronization of sampling and conduction, the sampling rhythm and the turn-off threshold are optimized in combination with feed-forward vibration suppression and residual adjustment, the short circuit identification speed and precision are improved, and the method has self-healing and self-correcting capabilities and is suitable for high-frequency and high-power density scenes.

According to the high-low voltage lead structure of the single-machine 48-pulse hydrogen production rectifier transformer, a left device body, a right device body and a self-coupling modulation device body are arranged in an oil tank of the single-machine 48-pulse hydrogen production rectifier transformer, the self-coupling modulation device body is connected with the left device body and the right device body at the phase angle difference of 7.5 degrees, and the self-coupling modulation device body is powered by a grid-side three-phase power source. Power sources of the left transformer body and the right transformer body are output through the self-coupling modulation transformer body, a phase shift phase with the phase angle difference of 7.5 degrees is arranged between the left transformer body and the right transformer body, and four rectifiers with 12 pulses and 15-degree phase difference can be dragged by the valve side of a single 48-pulse rectifier transformer, so that the one-to-four function can be effectively realized, and the power consumption is reduced. Meanwhile, the size and the weight of the system are effectively reduced, the overall manufacturing cost is greatly reduced, and rapid industrialization of green hydrogen is facilitated.

The invention discloses a distribution line fault point positioning method and device, and relates to the field of power distribution networks, and the method comprises the steps: constructing a plurality of virtual fault points, and determining the zero-sequence current before the fault point and the zero-sequence voltage of the fault point of each virtual fault point based on the head-end zero-sequence voltage, the head-end zero-sequence current and the tail-end zero-sequence current of a fault section; determining the phase difference between the zero-sequence current before the virtual fault point and the zero-sequence voltage of the virtual fault point; and taking the virtual fault point with the phase difference smaller than the judgment threshold as a fault point, and determining the fault distance between the fault point and the head end of the fault section. Because the zero-sequence voltage and the zero-sequence current of each virtual fault point have a phase constraint relationship, when the voltage phase and the current phase are approximate, the virtual fault point is proved to be an actual fault point. Therefore, a plurality of virtual fault points are constructed, the phase difference between the zero-sequence voltage and the zero-sequence current is respectively calculated, additional measurement equipment is not needed, and the calculation result is simpler.

The invention provides a current-limiting protection method and a current-limiting protection circuit. The current-limiting protection method comprises the steps of generating a preset wave-by-wave current value when an inverter is started and loaded, so as to carry out wave-by-wave current limiting on the inverter. And in the process of wave-by-wave current limiting, the phase difference between the phase current and the phase voltage of the inverter is obtained. And judging the load type of the inverter based on the phase difference between the phase current and the phase voltage. And adjusting the preset wave-by-wave current value according to the load type so as to match the load type. According to the invention, the load type of the inverter can be judged according to the phase difference between the phase current and the phase voltage, such as inductive, capacitive or resistive load. And then the preset wave-by-wave current value is adjusted according to different load types, so that the inverter can better adapt to loads with different characteristics. Namely, the wave-by-wave current value can be dynamically adjusted according to the type of the load, so that the inverter can adapt to the change of the load in time, and the operation stability of the inverter is improved.

A delay control method includes the following steps. A pre-N-value detection operation is performed comprising detecting a number of delayed clock cycles from an input clock signal to an output clock signal as a number of pre-delayed clock cycles before a delay operation is performed. A delay amount is set by a DLL control circuit according to a phase difference between the input clock signal and the output clock signal and the number of pre-delayed clock cycles. A control signal representing the delay amount is output by the DLL control circuit. The delay operation is performed by a delay line circuit according to the control signal, wherein the delay operation comprises delaying the input clock signal based on the delay amount and generating the output clock signal so that the input clock signal and the output clock signal are synchronous.

The precision capacitance micrometer system comprises a modulation signal source, a sensitive probe, a differential transformer bridge circuit, a signal amplification link, a multiplier and a low-pass filter circuit which are electrically connected in sequence, a double-limit comparator is arranged between the signal amplification link and the multiplier; the input end of the double-limit comparator is connected with the output end of the signal amplification link, the output end of the double-limit comparator is connected to one input end of the multiplier, and the double-limit comparator is used for shaping the amplified modulation signal and taking the shaped signal as the demodulation input signal. The invention also provides a precise capacitance micrometer method. The precise capacitance micrometer system provided by the embodiment of the invention ensures that the system output is insensitive to phase difference fluctuation within a certain demodulation phase difference range, and finally realizes high-precision measurement of micro displacement. All the modules complete full-link conversion from physical quantity to measurable voltage signals through step-by-step signal transmission and function complementation.