375 results about "Phase angle" patented technology

The invention belongs to the technical field of power system measurement, and relates to a three-phase power parameter wireless synchronous measurement and vector analysis method and system, and the method comprises the following steps: generating and broadcasting a synchronous pulse code containing triggering phase information; generating a predicted phase angle; obtaining a comprehensive phase deviation value; performing dynamic feature separation processing on the comprehensive phase deviation value to generate a slowly-varying propagation delay feature and a transient prediction error feature; injecting the prediction error characteristics into a local phase predictor for calibration; acquiring phase voltage / current data based on the compensated sampling time, and calculating a fundamental wave effective value and a phase angle relative to a local calibration time reference; and packaging the fundamental wave effective value, the phase angle and the local timestamp into a simplified data packet and transmitting the simplified data packet to an analysis terminal. According to the method, the problems that in a traditional mode, satellite time service rejects signals in a substation indoor or underground scene, and synchronization interruption is easily caused by electromagnetic interference are solved.

The invention relates to the technical field of cable fault monitoring, in particular to a power cable fault monitoring method and system based on big data, and the method comprises the following steps: carrying out the optimization and integration of spatial layout and sampling time based on a cable monitoring node, recognizing a data segment with the reverse trend of a current peak and a voltage phase angle, and carrying out the recognition of a current peak; and further analyzing the synchronism of the current-carrying density and the temperature, extracting a periodic intersection distribution characteristic, screening a continuously progressive trend track, and forming a trend directivity factor. According to the method, the linkage accuracy among multi-point signals is guaranteed by combining synchronous acquisition of node data with time sequence calibration, the trend discrimination method performs step-by-step screening for collaborative fluctuations of different characteristic parameters, and a continuous evolution sequence of various types of tiny disturbances under a complex working condition is dynamically extracted; a temperature and current-carrying density correlation mode is adopted to highlight the progressiveness and the positioning capability of a fault precursor, and dynamic risk signals which are difficult to identify at the initial stage of change are effectively captured.

The invention discloses a low-voltage distribution area topology identification method, system and device and a storage medium, and the method comprises the following steps: deploying a synchronous measurement unit in a low-voltage distribution area, and obtaining the outgoing line current phasor and voltage phasor data with a synchronous time scale of a whole network; constructing an incoming line and outgoing line current phasor set, and performing adaptive descending sorting according to amplitudes; determining that the nodes corresponding to the incoming line current phasors and the found nodes corresponding to the one or more outgoing line current phasors are in a father-son relationship, and iterating the process until all sets are empty, thereby completing the identification of the topological relationship of the power distribution side; and according to the equipment number contained in the obtained voltage phasor data, determining a meter box connected with the user electricity meters, and then clustering the user electricity meters connected to the same meter box according to the voltage phase angle to obtain the connection phase sequence of each user electricity meter. The problem of key information missing is solved from a data source, and accurate and efficient identification of topology is realized by fusing physical constraints.

The present application relates to the technical field of motors, and discloses a motor control method and apparatus based on harmonic injection, and a device and a storage medium. The method comprises: on the basis of a motor and noise of the motor, determining a specified-order harmonic wave needing to be injected; acquiring a rotational speed and torque of the motor, and determining a voltage magnitude and a phase angle of the specified-order harmonic wave corresponding to the rotational speed and the torque from a preset specified-order harmonic wave table; performing transformation processing on the voltage magnitude and the phase angle to obtain a target voltage value in a three-phase coordinate system; and superimposing the target voltage value onto a fundamental voltage to obtain a control voltage, wherein the control voltage is used for controlling the operating state of the motor. In the present application, torque harmonic waves generated by the driving of a motor are eliminated, thus significantly reducing the noise during the operation of the motor and a load system.

The invention discloses an improved flexible direct current fault control method for improving current differential protection adaptability, and belongs to the technical field of power system relay protection and new energy power generation system grid-connected control. The method comprises the following steps: detecting a voltage drop abrupt change signal and a negative sequence voltage signal of a flexible DC output end, and starting a control strategy when the signals are satisfied; detecting a terminal voltage signal and active power of a new energy sending-out terminal, and calculating a new energy side current phase angle and a power angle; calculating a flexible DC side current phase angle control value and a negative sequence dq axis current reference value based on the parameters; and controlling the flexible DC side to output a negative-sequence current corresponding to the negative-sequence dq-axis current reference value, so as to actively adjust the current phase of the flexible DC side, reduce the phase angle difference between the fault current of the flexible DC side and the fault current of the new energy side, and discriminate the internal and external faults of the region through traditional current differential protection. According to the invention, the degree of freedom is controlled and the current phase is adjusted by using the flexible direct-current side negative-sequence current to reduce the phase angle difference of the two sides, so that the problem that the current differential protection adaptability in the double-end weak feedback system is reduced is solved, additional hardware is not needed, and the power grid safety and the new energy stable grid connection are ensured.

The invention discloses a radial power distribution network topology identification method, system and device and a medium. The method comprises the following steps: acquiring node voltage amplitude measurement data; calculating a sample covariance matrix based on the voltage amplitude measurement data to obtain the covariance of the voltage amplitude between the nodes; estimating a precision matrix of the covariance matrix through a graph lasso model; calculating a partial correlation matrix based on the precision matrix, wherein the partial correlation matrix is used for representing a direct correlation coefficient between nodes in the radial power distribution network; and deriving an adjacent matrix through a maximum spanning tree based on the partial correlation matrix to obtain a radial power distribution network topological structure. According to the method, sparse learning and partial correlation analysis are combined to deal with the problem of limited data volume; the key condition dependency relationship between the nodes can be quickly and accurately identified only through voltage amplitude measurement data without a large number of samples and phase angle information, and the identification precision is high.

The invention provides a self-networking control protection method and device for a grid-connected energy storage converter, and a medium. The method comprises the following steps: acquiring electrical quantities of a grid-connected point and a direct current side, establishing a short-circuit capacity estimation value and a positive and negative zero sequence model, and generating a voltage phasor reference; generating a given frequency and a given voltage according to the power and frequency droop and the reactive power and voltage droop; generalized impedance shaping is executed in a control loop, and virtual impedance and selective filtering are configured according to frequency bands; completing grid connection or re-connection according to a sequence of frequency slope, phase angle slow alignment and voltage amplitude gradual combination based on a grid connection point reference phasor; setting positive-sequence, negative-sequence and zero-sequence fault current upper limits and a time sequence template in the symmetric component domain; and outputting the given frequency, the given voltage, the sequence component limit value and the protection state instruction to a converter power bridge driving and grid-connected switch control interface. According to the invention, phase-lock-free grid-connected synchronization, unified control protection switching, sequence component controlled fault current and weak grid stable operation can be realized.

The invention relates to the technical field of power systems, and discloses a wind and light output scene-oriented power system power flow data reconstruction method, system and device and a medium, and the method comprises the steps of constructing structured boundary input data; generating a voltage amplitude and a phase angle estimation vector of each node through a deep neural network model, and taking the voltage amplitude and the phase angle estimation vector as a power flow initial solution; performing physical constraint check on the initial solution, identifying out-of-limit nodes and determining an adjustable point set with reactive power regulation capability; and in the range of the adjustable point set, constructing an optimization function, solving to obtain a local adjustment quantity, correcting the initial solution, and generating a final power flow solution meeting the operation constraint of the power system. According to the method, data-driven modeling and physical constraint checking are fused, overall mapping is performed on a high-dimensional scene formed by wind and light output and load by using the deep neural network, the problem that the convergence performance is sharply reduced when the dimension is increased and the number of scenes is increased in a traditional iteration method is avoided, and rapid, stable and engineering-available power flow data generation is realized.

The invention relates to a DC networking new energy ship shore power grid-connected anti-disturbance control method and system, and the method comprises the steps: calculating an angular frequency and a phase angle based on a virtual synchronous generator model, inputting the angular frequency deviation into an extended state observer, and estimating the total disturbance in real time; performing feedforward compensation fusion on the original active instruction of the virtual synchronous generator and the total disturbance observation value to generate an anti-disturbance active power reference instruction; running SPWM modulation according to the direct current side signal and the active instruction, and generating a modulation signal to control power conversion; the driving signal is fed to a power grid after being amplified and filtered; meanwhile, output current is collected and compared with reference current synthesized by phase angles, zero static error tracking is achieved through a quasi-proportional resonance controller, and compensation signals are generated for real-time correction modulation; the grid-connected power converter adopts a new-generation power electronic switching device SiC-MOSFET, and the efficiency can exceed 98%. Compared with the prior art, the system has the advantages of high stability, high electric energy quality, high reliability and the like.

The invention discloses a measurement method for accelerated calorimeter test based on in-situ electrochemical impedance spectroscopy. The measurement method comprises the following steps: applying excitation current to a battery to be detected; measuring the battery to be detected under the current condition through the EIS module to obtain real part impedance and imaginary part impedance under different frequencies; determining phase angles and impedances under different frequencies according to the real part impedances and the imaginary part impedances under different frequencies; the voltage of the battery to be detected at different surface temperatures is collected through the ARC module, and the corresponding temperature rise rate is determined; determining an impedance modulus deviation, a phase deviation, a voltage sharp change deviation and a temperature rise rate deviation according to the phase angles and the impedances under the different frequencies, the voltages under the different surface temperatures and the corresponding temperature rise rates, and generating an error signal; generating a corresponding sampling rate control instruction according to the error signal based on dynamic PID control; and the ARC module adjusts the sampling frequency according to the sampling rate control instruction so as to perform high-precision measurement.

The invention discloses a conductive slurry production control method and system based on multi-parameter cooperative control, and relates to the field of conductive slurry production, and the method comprises the steps: obtaining rheological characteristic data; according to the rheological characteristic data, a zero crossing point time difference between the excitation signal and the response signal is extracted, and a rheological phase angle is calculated; whether the rheological phase angle is located in a preset optimal dissipation interval or not is judged; if yes, the intrinsic relaxation time of the slurry microstructure is determined, and compensation frequency is generated according to the intrinsic relaxation time; the compensation frequency is used as a perturbation signal to be superposed to a driving voltage waveform of a driving motor, so that the stirring blades generate high-frequency vibration; and acquiring the deviation direction of the rheological phase angle, and dynamically adjusting the speed ratio of the revolution speed of the revolution shaft to the rotation speed of the rotation shaft under the condition of keeping the total power unchanged, so as to lock the rheological phase angle in the optimal dissipation interval. According to the invention, the yield and reliability of the electronic product can be effectively guaranteed.

The invention discloses a method for accurately measuring voltage, current and phase angles of a sectional intelligent electric energy meter, which relates to the technical field of electric energy meter metering and comprises the following steps of: S1, constructing a sectional load-mutual inductor angle difference correlation model, and dividing a plurality of load intervals according to an application scene of the sectional intelligent electric energy meter and working characteristics of a mutual inductor, acquiring current transformer angular difference data and voltage transformer impedance drift related data in different load intervals, and establishing and storing an association relationship between each load interval and a corresponding transformer angular difference compensation coefficient in combination with inherent parameters of the transformer; according to the invention, a segmented load-mutual inductor angle difference correlation model is constructed in advance, load voltage and current amplitude data are collected in real time to accurately determine a current load interval, and a corresponding mutual inductor angle difference compensation coefficient is automatically matched to carry out dynamic adaptive compensation on an initial phase angle. The problem of phase deviation caused by angular difference nonlinear change of a current transformer in different load intervals and impedance drift of a voltage transformer in the prior art is solved.

The invention discloses a phase sequence self-adaption method and device for a three-phase grid-connected converter, equipment and a medium, and relates to the technical field of three-phase electricity. The phase sequence adaptive method of the three-phase grid-connected converter is applied to a three-phase grid-connected converter system. The method comprises the following steps: acquiring a phase angle of a voltage of a first detection point and a voltage of a second detection point; and determining a correct phase sequence of the voltage of the second detection point according to the voltage of the second detection point and the phase angle of the voltage of the first detection point. The initial phase sequence of the input voltage signal can be rapidly and accurately detected, the operation logic is simple, the operand is small, and implementation is easy.

The invention provides a high-power rectification resonance control method and system for a quick charger, relates to the technical field of rectification resonance, and aims to obtain direct-current bus voltage, adjust output power through frequency modulation of a full-bridge LLC resonant converter, and perform voltage stability control adjustment in combination with feedback current data. Charging curve data analysis is carried out to acquire charging key nodes and resonance frequency nodes, device state data acquisition and analysis are carried out, a frequency conversion control loop is constructed, resonance frequency adjustment is carried out, after adjustment is completed, abnormal nodes are identified and combined analysis is carried out, optimal parameters of each load segment are acquired, and voltage fluctuation data are acquired. The method comprises the steps of carrying out fluctuation influence analysis, carrying out fluctuation suppression by adjusting a switching frequency and phase shift angle combination of a full-bridge LLC resonant converter, carrying out calculation through the full-bridge LLC resonant converter to obtain an equivalent voltage control instruction, carrying out mode buffer switching and obtaining mode control switching data, and realizing rectification resonance accurate control of the charger.

The invention discloses a multi-mode fault ride-through control method of a network-forming type energy storage converter, which relates to the technical field of converter control and comprises the following steps of: acquiring node voltage amplitude, voltage phase angle, system frequency and harmonic component, and filtering acquired data; according to the method, the operation region is calculated based on the real-time filtering data, the electromagnetic transient energy and the rotation kinetic energy component, so that the network-forming type energy storage converter intelligent body at different spatial positions can obtain differentiated control margins during the fault period; the operation area of the network-forming energy storage converter intelligent body which is close to a fault point and is seriously influenced by voltage sag or frequency fluctuation can automatically contract during a fault period; the operation area of the network-forming type energy storage converter intelligent body which is far away from the fault point and is slightly disturbed by the fault is kept relatively loose, and the technical problems that control close to the fault point is insufficient and control resources far away from the fault point are wasted due to one-time cutting of a traditional fixed operation area are effectively solved.

A method is for adaptively controlling a charging module that converts three-phase AC input to DC output with improved power factor correction. The method includes performing Clarke and Park transforms on input three-phase AC voltages to obtain d-q axis components, measuring and transforming boost inductor currents to obtain current axis components, generating control values through current-loop and voltage-loop modules based on target and measured values, and synthesizing PWM signals to control switching operations. The method features adaptive phase angle computation using a proportional-integral controller that responds to load variations in real-time. The control system maintains high power factor under varying load conditions by continuously adjusting the phase reference based on the q-axis voltage error. This approach minimizes power losses, reduces harmonic distortion, and ensures stable operation across the full operating range of the charging module while maintaining unity power factor.

The invention belongs to the field of electric energy meters, particularly relates to an automatic compensation calibration method for electric energy metering errors of an electric energy meter, and aims to solve the technical problems that a CORDIC algorithm is difficult to give consideration to efficiency and precision and an existing compensation method is difficult to correct multi-dimensional nonlinear errors under wide temperature and wide flow. Outputting an uncorrected x-axis component and a final accumulated phase angle, wherein the improved CORDIC iterative operation comprises M times of coarse rotation iteration and P times of fine rotation iteration; s2, performing amplitude correction on the uncorrected x-axis component to obtain a corrected instantaneous current amplitude; and S3, performing reconstruction by using the corrected instantaneous current amplitude and the final accumulated phase angle to obtain a corrected instantaneous current value, multiplying the corrected instantaneous current value by the instantaneous voltage value to obtain instantaneous active power, and performing accumulated integration on the instantaneous active power to obtain a compensated and calibrated electric energy value. According to the invention, high-precision metering performance of the electric energy meter in a wide current range and a wide temperature change range can be ensured.

The invention relates to the technical field of line loss assessment, in particular to a power system line loss assessment method and system based on big data processing, and the method comprises the following steps: collecting voltage, current and phase angle signals of a power supply section, carrying out the frequency domain transformation, extracting the amplitude and phase of a frequency component, and generating a frequency spectrum feature set; energy spectrum characteristics and a migration sequence are calculated to analyze spectrum form stability, a risk section is identified by combining a power flow direction and an energy migration included angle difference, and a line loss assessment result is generated by combining a gravity center drift trend and an energy change sequence. Energy spectrum features and migration sequences are extracted to describe power grid energy distribution changes, an included angle difference between a power flow direction vector and an energy migration direction is calculated to screen an abnormal section, an energy drift trend is analyzed in combination with a frequency spectrum gravity center track, line loss real-time quantification and area positioning are achieved, and abnormal loss identification precision and operation evaluation stability and reliability are improved.

The invention discloses a method for identifying abnormal parameters of a low-voltage transformer area based on dynamic Bayesian optimization. The method comprises the following steps of: acquiring total active and reactive power of head-end voltage amplitude phase angles and active and reactive power of each phase at the tail end of a three-phase asymmetric line; configuring a distribution network load flow calculation model; based on the parameter combination, calling three-phase unbalanced load flow calculation to construct a weighted loss function of total active power and reactive power deviation; iteratively updating R1 and R0 to drive load flow calculation by adopting a dynamic Bayesian optimization algorithm until a loss function is converged; and judging the topology anomaly type according to the deviation between the optimization parameter and the standard value. According to the method, the three-phase unbalanced power flow model and the dynamic Bayesian optimization algorithm are fused, the accuracy rate of abnormal parameter identification of the low-voltage transformer area is effectively improved, the problem that an existing method is poor in adaptability to topological dynamic changes of the transformer area is solved, and meanwhile the method is based on physical parameter deviation analysis of the positive-sequence resistance and the zero-sequence resistance, and the identification accuracy of the abnormal parameters of the low-voltage transformer area is improved. An interpretable decision-making mechanism is constructed, and direct positioning of fault types is realized.

The invention discloses a hybrid CGAN-based power system forced oscillation source positioning method, and the method comprises the steps: inputting to-be-recognized data into a trained CNN classifier, and obtaining an oscillation source recognition result; wherein the CNN classifier is trained according to the mixed data set; the mixed data set is constructed according to FO generation data generated by the trained mixed CGAN and real data; the FO generation data is false forced oscillation data; each group of real data comprises active power, reactive power, voltage amplitude and voltage phase angle; the hybrid CGAN is obtained according to the CNN, the BiLSTM and the attention mechanism. According to the method, the convolutional neural network, the bidirectional long-short-term memory network and the attention mechanism are fused into the generator and the discriminator of the CGAN, so that the similarity between the FO generation data and the real data is improved, the FO generation data and the real data are used for training, and the precision of forced oscillation source positioning can be effectively improved.

The invention discloses a method for predicting the service life of an arc extinguishing device of a low-voltage circuit breaker. An arc extinguishing chamber is divided into a left arc starting area, a middle motion area and a right arc extinguishing area along an arc motion path; configuring a special multi-mode sensor group for each section, and respectively acquiring physical signals related to the core degradation mechanism of each section; extracting characteristic parameters including an arcing phase angle, an arc movement speed and an air pressure rising rate from the signal, and calculating an efficiency coefficient of each section; based on the efficiency coefficient and the accumulated stress, establishing an independent exponential attenuation model for each section to calculate the accumulated degradation amount; and finally, the maximum accumulated degradation amount in the three sections is taken as a system health state index, and accurate prediction of the residual life is realized. According to the method, the problems that a prediction object is fuzzy and a fault cannot be positioned in a traditional method are solved, the crossing from overall early warning to accurate section diagnosis is realized, and an effective means is provided for predictive maintenance of the low-voltage circuit breaker.

The invention relates to the field of electrical equipment detection, in particular to a transformer partial discharge detection method and system based on optical signal characteristics. The method comprises the following steps: acquiring an optical signal generated by partial discharge in the transformer and converting the optical signal into a voltage pulse signal; synchronizing the signal with the power frequency voltage of the transformer, and recording the peak amplitude of each pulse signal and the corresponding power frequency voltage phase angle to form a discharge data point set; carrying out statistical distribution analysis on the phase angles of the data points in a power frequency period of 0-360 degrees, and extracting a characteristic phase interval representing a discharge phase aggregation rule; and matching the characteristic phase interval with a predefined discharge type discrimination rule, and determining the partial discharge type. The method solves a problem that a conventional optical detection method cannot accurately recognize the partial discharge type of the transformer, is high in electromagnetic interference resistance, and improves the detection precision and engineering practicality.

The application discloses a high-precision model prediction current control system and control method of a double three-phase motor, and relates to the technical field of multiphase motor control. The application extends the traditional 12 virtual voltage vector control set, designs 24 virtual voltage vectors with equal amplitude and uniform phase angle under the premise of not losing voltage utilization rate, and improves control precision. A duty cycle calculation method based on minimum error is proposed, which can track the currents of d-axis and q-axis at the same time even in the case of a single effective virtual voltage vector, and guarantees optimal output duty cycle. In addition, the process of traversing all voltage vectors in the prediction control is simplified, and the calculation burden of the algorithm is reduced. The application improves the precision of model prediction control by extending the control set and reducing the calculation error of the duty cycle, reduces 5th and 7th harmonics, and improves torque ripple. Moreover, even under the action of 24 voltage vectors, the calculation amount is still low, and the execution efficiency of the algorithm is improved.

The application discloses a power distribution network fast protection method and device and a computer readable storage medium, wherein the method comprises the following steps: S1, sequentially calibrating branch lines of a radial power distribution network to determine the grades and numbers of the feeder branch lines; S2, constructing a starting criterion by using transformer low-voltage side currents to calibrate the moment of fault occurrence; S3, according to different fault types, selecting characteristic phases and calculating the amplitude and phase angle of the corresponding characteristic phase mutation current phasor; S4, taking the main transformer low-voltage side phasor as a reference phasor, calculating the inner product of the phasor calculated by other lines and the reference phasor respectively, and marking all the lines with inner product greater than the setting value; and S5, finding the line with the highest number and grade among all the marked lines and marking the line as a fault line. The application can solve the contradiction between the four properties of the traditional power distribution network three-section current protection, and well cope with many problems such as high resistance fault and slow backup protection action.

The invention discloses a fault component compensation type low-voltage ride-through control method and system of a distributed power generation system and a storage medium, and the method comprises the steps: introducing a difference value between a d-axis voltage instantaneous component of a common coupling point and a system rated voltage into a quadrature-axis voltage compensation branch during the voltage drop period of a power grid, and obtaining a quadrature-axis voltage compensation amount through compensation coefficient calculation, the calculation result is added to the phase-locked loop control link, the q-axis voltage of the common coupling point tracked by the phase-locked loop is adjusted in real time, and the problem that the phase angle of the distributed power generation system is prone to loss stability during the transient state is effectively solved without any additional control information. And the low-voltage ride-through capability of the distributed power generation system under the extreme working condition is obviously enhanced.

The application discloses an asymmetric phase-shifting control method suitable for a half-wave shaping MMC, and can realize wide-range operation energy balance of a converter. The method is characterized in that, in a 2pi period, a commutation unit switching function and a multi-level unit modulation voltage are not switched in a half-wave period pi, but in a positive half-wave mode, [0, pi] is taken as a reference to expand and shift an angle theta to the left and right, that is, the interval is [-theta, pi+theta], and in a negative half-wave mode, [pi, 2pi] is taken as a reference to shrink and shift an angle theta to the left and right, that is, the interval is [pi+theta, 2pi-theta]. The application adopts an asymmetric phase-shifting modulation method, generates and reverses polarities of two asymmetric partial sine waves through a commutation switch cooperating with a multi-level unit, and obtains a complete multi-level sine wave on an alternating current side. The application can eliminate the limitation of a power factor angle on a phase-shifting angle while realizing wide-range energy balance of the converter, is only affected by a modulation ratio, and compared with symmetric phase-shifting modulation, is beneficial to simplifying commutation control logic when the system is in a wide-range reactive power regulation, and has better engineering application value.

Certain aspects of the present disclosure provide techniques for determining a topology of an electric vehicle supply equipment (EVSE) network. An example method includes obtaining, for a first time period, for each of a plurality of pieces of equipment of the EVSE network, a respective magnitude of a respective current phasor, wherein for each of one or more pieces of equipment of the plurality of pieces of equipment, a respective phase angle of the respective current phasor is unknown; and determining, based on at least the respective magnitude of the respective current phasor for each of at least one piece of equipment of the one or more pieces of equipment, a respective subset of lines of the EVSE network to which the respective piece of equipment is coupled.

A method is provided for reducing common mode voltages in a system that includes an inverter connected to a motor by a long cable by controlling switches of the inverter to generate voltage vectors that emulate a three-phase sinusoidal waveform by switching between adjacent active vectors and active vectors that are separated by 180 degrees, determining whether a phase angle of the vectors is increasing or decreasing, determining a decision angle within the sector which is a function of a duty cycle offset and a modulation index; and applying duty cycle manipulation rules, including: responding to an increasing phase angle that is less than the decision angle by setting a duty cycle of the adjacent active vectors to a duty cycle high value; and responding to an increasing phase angle that is greater than 60 degrees minus the decision angle by setting the duty cycle to a low value.

A state detection method detects a state of an oil film formed by a lubricant in an apparatus configured to lubricate a plurality of sites with the lubricant, the state detection method having: a measurement step of measuring an impedance and a phase angle of a circuit composed of the plurality of sites by applying an alternating voltage to the circuit while varying a frequency; and a derivation step of deriving an oil film thickness formed by the lubricant and a parameter representing an electrical characteristic at the oil film thickness, based on a relative dielectric constant of the lubricant at a high frequency limit and the measured impedance and phase angle.

The application provides a power system stability analysis method based on impedance measurement data, comprising determining that the current analysis condition is a condition corresponding to an equivalent circuit diagram based on a converter topology structure diagram, wherein a disturbance voltage source is in series or a disturbance current source is in parallel; under the current analysis condition, disturbance voltage components and disturbance current components generated on the converter side are obtained to obtain converter impedance measurement data carrying amplitudes and phase angles at several frequency points, and disturbance voltage components and disturbance current components generated on the power grid side are obtained to obtain power grid equivalent impedance measurement data carrying amplitudes and phase angles at several frequency points; the converter impedance measurement data and the power grid equivalent impedance measurement data at the same frequency point are compared, and according to each comparison result, the risk of oscillation instability of the power system is judged. The application is implemented to reduce the complexity of impedance measurement operation, thereby improving the analysis accuracy.