112 results about "Harmonic function" patented technology

The invention relates to the field of electric energy quality monitoring, aiming to solve the problem that user-side harmonic pollution can not be correctly obtained in the prior art. The invention provides a method and a system for monitoring the user-side harmonic pollution. The method comprises the following steps of: collecting current data of a user-side electrifying apparatus by utilizing a current collecting device; collecting public connection point voltage data by utilizing a voltage collecting device; transmitting the current data and the public connection point voltage data to a system terminal; calculating the current data of emission harmonic of the user-side electrifying apparatus and an impedance value of the harmonic of the electrifying apparatus at the system terminal by utilizing a partial least-squares regression algorithm to acquire active power of the emission harmonic of the user-side electrifying apparatus; and sending alarming information when the active power of the emission harmonic exceeds the preset threshold. The invention has the advantages of conveniently monitoring the pollution to power grid by the user-side electrifying apparatus to reduce fluctuation of the power supply quality of the power grid.

The invention relates to a system for harmonic detection and control of an APF (active power filter) based on windowed all-phase FFT (fast Fourier transform), which comprises an alternating-current power grid with a nonlinear load and an active current filter, and is characterized by also comprising a control module and a detection module. A working method comprises: signal detection, command triggering, pulse uttering and generation of compensating current. The system and the method have the advantages that (1), the system is simple and the cost is medium; (2) the frequency, the amplitude and the phase of the harmonic current can be detected in an accurate and real-time way, and the compensating performance of the APF can be guaranteed; (3) the accuracy and the real-time performance of calculation can be improved; and (4) the current tracking control effects of the APF can be improved.

There are provided visual displays for graphically showing on a visual representation of a guitar fretboard a location relationship between a given chord and its chord tones as well as for graphically showing on a visual representation of a guitar fretboard a location relationship between a given position and its scale tones. The present disclosure also relates to a method for visually expressing, on a visual representation of a guitar fretboard, the location relationship between a given chord, its chord tones and its scale tones, in a given key; a music notation method for representing a location relationship between a given chord, its chord tones and the scale tones of the scale to which said given chord belong, on a visual representation of at least a portion of a guitar fretboard; and visual display for expressing musical harmonic functions.

The invention provides a harmonic source identification method which comprises the following steps: performing responsibility allocation on harmonic pollution through the harmonic voltage emission level of a user, wherein the harmonic voltage emission level of the user at a time is represented through the variable quantity of harmonic voltage or current at a time at a point of common coupling before and after the user accesses to a power system; positioning an accurate point of a harmonic source through harmonic emission level evaluation to the maximum extent. The method has the benefits that an algorithm provided by the invention can quickly determine the harmonic source, is high in accuracy and practicality, and has very good project utilization values.

The invention discloses a GNSS ionization layer delay precise modeling method suitable for a Chinese region. The geographical coordinates of the latitude and the longitude of a cross point are converted into coordinates under an established spherical crown coordinate system, so as to acquire the range of the latitude and the longitude of the cross point under the spherical crown coordinate system. The change range of the latitude and the longitude of the cross point is projected and converted into a global coordinate system. A spherical harmonic function is used to establish a regional ionization layer total electron content (TEC) model. The ionization layer delay precise modeling method suitable for the Chinese region is constructed. Compared with the existing method, the method provided by the invention has the advantages that through rotation projection and conversion, the distribution of the ionization layer cross point meets the requirement of the spherical harmonic function on physical quantity distribution in the form; ill-conditioned problems are solved when the spherical harmonic function is applied to regional modeling; the precise describing ability of the spherical harmonic function for global change physical quantity is effectively used; non-integral order in a spherical crown harmonic function is avoided; and the complexity of ionization layer TEC modeling calculation is reduced.

The invention discloses a method for measuring electric energy of a harmonic power network. The method comprises the following steps of: collecting harmonic content and harmonic waves injected in the power network by a user; calculating the total harmonic distortion (THD) of harmonic waveforms at different time intervals, judging a relationship between the THD and a preset waveform distortion factor threshold value, and respectively calculating the electric energy in different measuring modes. A threshold value (referring to a national harmonic standard limit) is set according to different THDs under harmonic conditions so as to distinguish that the user is a harmonic user or a non-harmonic user in different measuring modes, if the harmonic influence is large, and the user serves as a linear user, the sum of electric energy of the consumed fundamental waves and harmonic waves is calculated, and simultaneously the electric energy of the harmonic waves injected into the power network is recorded so as to be used as a technical reference index; and if the harmonic influence is extremely large and belongs to a typical harmonic source load, the sum of absolute values of the electric energy of the consumed fundamental waves and harmonic waves and the harmonic waves injected into the power network is calculated, and an aim of controlling the harmonic waves is fulfilled finally.

A method of tip clearance estimation for a rotor blade is provided. The method includes measuring blade deflection of the rotor blade, generating a harmonic function for the rotor blade from the measured blade deflection, predicting tip displacement of the rotor blade using the generated harmonic function and adjusting a position of the rotor blade according to the predicted tip displacement.

The invention provides a periodic detection method and system for a GNSS observation station coordinate time sequence. The method comprises the steps of acquiring a GPS observation station coordinatetime sequence observed value, removing gross errors and correcting an antenna phase center deviation; performing preliminary spectrum analysis on the GPS observation station coordinate time sequence by using a periodogram method; acquiring a plurality of major cycle frequencies of a corresponding observation station, and sorting according to the amplitudes of main frequencies; describing the GPS observation station coordinate time sequence by using a harmonic function, acquiring a harmonic function model of the GPS observation station coordinate time sequence, and building a harmonic functionmodel matrix; using the main frequencies as prior constraints, and acquiring the standby frequencies of a plurality of periodic signals; resolving the harmonic function model based on a least squarescriterion, acquiring optimal frequencies and verifying the standby frequencies by using a hypothesis testing method, and building the harmonic function model including the plurality of optimal frequencies; and according to the standby frequency after hypothesis testing is performed, resolving the harmonic function model matrix based on the least squares criterion, and acquiring a detection resultof any GNSS observation station periodic signal.

The invention discloses a time difference measuring method for communication signals with frequency shift and belongs to the field of passive positioning of radiation sources. According to the characteristic that sequence of autocorrelation function ratios of received signals at two different positions is a single-harmonic function of frequency shift parameters, the two-dimensional parameter estimation problem of the frequency shift and time difference is changed into two one-dimensional parameter estimation problem. The time difference measuring method for communication signals with frequency shift includes determining baseband signals generated after digital down conversion of the received signals at the two different positions and respective autocorrelation functions of the baseband signals; obtaining initial frequency shift estimation value through Fourier conversion by the autocorrelation function ratios, and obtaining accurate estimation values by Chirp-Z conversion; determining frequency shift compensation to a second channel of baseband signals; and determining cross-correlation functions of a first channel of signals and a second channel of signals, looking for the maximum value to obtain initial time difference estimation value, and obtaining accurate estimation value of time difference to the cross-correlation functions by Chirp-Z conversion. The time difference measuring method can accurately quickly measure time difference for the communication signals with frequency shift and is widely applied to a signal passive positioning system of communication radiation sources.

The present invention relates to an oil-immersed transformer overtemperature warning method under a harmonic condition. The method comprises a step of determining any harmonic current distribution and the transformer winding eddy current loss, transformer stray loss and transformer total load loss actual values of a same total current effective value, a step of determining the relation among a transformer load loss, a harmonic distortion rate and a load rate, a step of determining the relation among a transformer hottest point temperature rise, the harmonic distortion rate and the load rate, and a step of determining the threshold of a corresponding alert level. According to the method, through transforming the basic formula of the transformer harmonic loss, the relation among the harmonic loss, a harmonic current distortion rate and the load rate is obtained, thus according to the relation model between transformer temperature rise and loss, the temperature rise condition of a transformer after a certain time is derived, and the early warning of the transformer temperature rise is realized.

The invention discloses a control strategy for restraining circulating currents of three-phase four-leg inverters on the basis of third-harmonic injection, and provides a method for restraining circulating currents of three-phase four-leg inverters on the basis of third-harmonic injection. The method includes that three-phase current reference signals outputted by voltage loops are synthesized into a zero-sequence current reference signal (4) on the basis (1) of parallel-connection voltage and current double-loop control of the three-phase four-leg inverters for a parallel-connection topology of two three-phase four-leg inverter modules (2) and (3), and error amplifiers track the zero-sequence current reference signal for a mid-line inductive current in a fourth leg of each module, so that mid-line currents of the two three-phase four-leg inverters are shared, and purposes of restraining the circulating currents of the mid-line currents, protecting power tubes and improving the efficiency of each inverter are achieved; and output signals of current loops of the two modules are synthesized to form two third-harmonic signals (5), the two third-harmonic signals (5) are added to obtain a sum (6), an average value (7) of the sum is used as a common third-harmonic signal (8) for being injected into three-phase and mid-line modulation signals of the two inverter modules, zero-sequence modulation components in the third-harmonic signals are eliminated, and the instantaneous zero-sequence circulating currents caused by factors such as inconsistency of parameters of a main circuit filter and inconsistency of switching time of switching tubes are restrained. The method has the outstanding advantages that the circulating currents of the mid-line currents are effectively restrained; control loops are simple; and third-harmonic injection of the parallel-connection inverters is unaffected, and the direct-current voltage utilization rate is increased.

The invention discloses an appointed subharmonic compensation APF (active power filter) and a harmonic detection and control method thereof. The APF comprises a signal sampling module (1), a human-computer interaction interface (2), an appointed subharmonic current detection module (3), a current tracking control module (4) and a power circuit module (5), wherein the signal sampling module transmits a collected signal to the appointed subharmonic current detection module; the human-computer interaction interface is connected with the appointed subharmonic current detection module; the appointed subharmonic current detection module is connected with the power circuit module via the current tracking control module. According to the APF, one or multiple times of harmonic of the harmonic current generated by load in a power grid can be appointed to carry out harmonic separation detection and compensation by the human-computer interaction interface, and various different working condition requirements can be satisfied in a flexible working mode. With the method, the stability and the reliability of harmonic detection and compensation current are enhanced so as to enhance the system stability and improve the system reliability.

The present invention discloses a GNSS position time series periodic characteristic mining method, and provides an accurate GNSS position time series periodic signal analysis and characteristic analysis method by considering the limitation of a conventional harmonic function, and introducing the methods, such as the wavelet analysis and FAMOUS time-frequency analysis methods, a maximum likelihood estimation method, etc. The method is characterized by decomposing an original time series into new time series of different frequency bands according to the different inherent frequencies of the different signals in the original series, and decomposing and reconstructing the signals, processing each layer, thereby obtaining a needed part. The method of the present invention overcomes the limitation of a conventional GNSS time series model, facilitates reflecting the periodical change of a coordinate series really, enables the precision and the reliability of the GNSS topocentric coordinates to be improved further, obtains the high-precision position and speed parameters, and provides the bases for knowing the influence mechanisms and the change rules of the relevant geophysical phenomena deeply.

The invention discloses a DFT harmonic detection method without an accumulated error sliding window. The DFT harmonic detection method includes: collecting voltage signals of a power grid, and utilizing digital phase-locked loop technology to enable voltage of the power grid to be synchronous; performing DFT forward transformation on collected load current signals x(t) through a sliding window iteration method to respectively acquire x-axis and y-axis components; determining instruction signals of hth harmonic waves, and utilizing DFT reverse transformation to extract each harmonic instruction. By the DFT harmonic detection method, the problem of extraction of realtime harmonic instructions of an active power filter is solved, and each harmonic component can be detected accurately and quickly to guarantee realtime compensation effect of the active power filter.

The invention relates to a method for controlling a parallel power quality regulator through non-harmonic detection. A main circuit is only composed of a three-phase LCL filter and a three-phase IGBT inverter bridge and is connected to the output end of a three-phase power grid. The three-phase IGBT inverter bridge is composed of a three-phase IGBT bridge and a direct current side capacitor. Harmonics, negative sequences and unbalance of load currents do not need to be detected through a complex detection algorithm, only the load currents need to be sampled, active current components in the load currents are offset through direct current side voltage stabilizing commands, and then harmonic, negative sequence and unbalance current commands are acquired. The complex detection algorithm is omitted, errors and time delay caused by the detection algorithm are avoided, and the dynamic response speed is increased; meanwhile, resources of a control chip are saved, and economical efficiency is improved. Compared with an existing active power filter, an existing static var generator and an existing static synchronous compensator, the parallel power quality regulator has certain advantages, certain practical value and certain application prospect.

The invention discloses an electric energy quality mixing detection method. The method comprises the following steps of using an inter-harmonic detection method based on a complex modulation refinement spectrum analysis method to detect interharmonics in a power grid; using a voltage fluctuation demodulation method to measure voltage fluctuations in the power grid; and using a flicker measurement method based on chirp Z transform to measure flickering in the power grid. An electric energy quality detection operand is reduced, real-time performance of inter-harmonic detection is increased and a flicker measurement error is eliminated maximumly. The chirp Z transform is used to calculate a frequency and an amplitude of a fluctuation component. An disadvantage that the flicker detection has a large error in a low frequency band is overcome. An effective support is provided for electric energy quality detection result correctness.

The present invention enables non-musicians to effectively compose music using a computer, and provides them with the means to manipulate musical content in an intuitive fashion without the need for formal musical training. The invention combines a representation of musical knowledge with a representation of musical data in such a way that permits transposition of the data to be constrained to conform to a set of harmonic rules. The user can select pitches to be moved higher or lower, and a system insures that it sounds good (where good is defined to mean "satisfies the conditions of the harmonic rule base").

The invention provides an image recognition method and device based on non-negative low-rank representation and semi-supervised learning. The method includes the following steps that: an image data set is obtained, wherein the data set contains marked data and unmarked data; an objective function is obtained according to a Gaussian field, a harmonic function and a low-rank representation function,non-negative constraint is performed on the coefficient of the low-rank representation function, the objective function is converted into a Lagrangian function, and variables, Lagrangian multipliersand a penalty factor in the Lagrangian function are updated; and iterative updating is carried out continuously until the method terminates, and the label matrix of the image data set is outputted, and test data are classified and identified according to the label matrix. According to the image recognition method and device of the invention, the semi-supervised learning and the low-rank representation are combined, and therefore, global structure information and local structure information can be well utilized, and the corruption of samples can be effectively eliminated or mitigated. The method and device have high robustness to noises and can obtain high classification performance regardless of whether training samples or test samples are damaged.

The invention provides an appointed sub-harmonic detection and compensation method with a reactive compensation function. Any sub-harmonic of harmonic current, generated by load in a power grid, is subjected to separated detection and compensation by abc-dq and dq-abc rotary coordinate conversion matrixes, and does not need to be subjected to calculation and detection respectively under the coordinate conversion of positive and negative sequences. According to the appointed sub-harmonic current detection method, the harmonic can be detected and compensated in a targeted manner and the method has the reactive compensation; the detection method is simpler and clearer. The compensation current can be controlled very well, and the control is easier to control. The system stability and reliability can be enhanced.

The invention discloses a method for removing cloud noise effects in a normalized difference vegetation index (NDVI) time sequence image. The method comprises the following steps of: S1, generating an annual NDVI time sequence image according to NDVI data of every ten days; S2, carrying out least square fitting on all time sequence pixels in the NDVI time sequence image, and assigning same values to weights of all points relative to a curve; S3, comparing an observed value with a fitted value, and eliminating points under negative cloud action; S4, repeating the steps S2 and S3, eliminating all the points under the negative cloud action, and generating a new curve; and S5, post-processing the curve obtained in the S4 to obtain a finally fitted curve. In the method disclosed by the invention, by utilizing an NDVI time sequence file and a harmonic function analysis method based on the least square fitting, cloud shielding and atmospheric effects on a sensor in a data acquisition process are effectively removed, the time sequence image with cloud contamination removed can be generated, the obtained curve has the advantages of obvious trend, strong relative property among years and high precision, and the method has a wide applicable range.

The invention discloses a harmonic voltage responsibility measuring method based on harmonic power monitoring. The harmonic voltage responsibility measuring method comprises the following steps of a step 10), acquiring an electric operation parameter of the system; a step 20), calculating a harmonic impedance of the system, namely calculating the harmonic impedance of the system according to the electrical operation parameter acquired in the step 10); a step 30), acquiring harmonic testing data, and forming a harmonic testing data set; a step 40), determining a harmonic current vector, namely calculating an angular phase difference between the harmonic current and the harmonic voltage based on the harmonic testing data acquired in the step 30); and a step 50), measuring the harmonic voltage responsibilities, namely measuring the harmonic voltage responsibilities at the user side and the system side according to the system harmonic impedance obtained in the step 20) and the harmonic current vector obtained in the step 40). The harmonic voltage responsibility measuring method has advantages of accurately dividing the harmonic voltage responsibilities at the system side and the user side, and facilitating targeted treatment to harmonic pollution of a power grid.

The invention provides a noise suppression method for a magnetic field sensor network. In the noise suppression method, by using a magnetic field sensor array, in virtue of the characteristic that signals are produced by an interference source and a signal source at nodes of the sensor network, magnetic field signals measured at the nodes of the sensor network are decomposed into superposition of a plurality of harmonic functions by using spherical harmonics, a vector signal base with linear independence is formed, the signal base is used for decomposing the measured magnetic field signals, the signal amplitudes corresponding to a signal source and a noise source are separated, and the signal amplitude corresponding to the noise source is abandoned, so that noise generated by the magnetic field noise source is suppressed.

The invention relates to a similarity-based semi-supervised learning spam page detection method, which solves the problems in semi-supervised learning through page links. A hidden 'link' diagram is established based on page similarity in the method. The method comprises the following steps: 1, extracting page features based on contents and links; 2, carrying out feature extraction for features extracted in Step 1 in a method of principal component analysis; 3, establishing a hidden 'link' diagram according to the page similarity; 4, building a Gaussian random field model on the 'link' diagram, and carrying out semi-supervised learning through harmonic functions; and 5, combining classification results of the model established in Step 4 and other classifiers, thereby improving the classification effect. In the diagram, the weight is given to the links between pages according to the similarity, the Gaussian random field model is then established, and the harmonic functions are adopted for semi-supervised learning, thereby improving the semi-supervised learning capacity.