120 results about "Power system harmonics" patented technology

The invention discloses a method for computing harmonic impedance of a power system, and belongs to the field of designs for methods for computing harmonic impedance. The technical scheme includes that a complex least square method is introduced into the subject of computation of harmonic impedance of a power system, and phasor real parts and imaginary parts of measured voltage, measure current and the like are used as organic integration to be computed, so that the optimized least square solution is obtained. Raw data are screened by a method on the basis of relative complex residual error sorting while the data are introduced and processed, and influence of abnormal points to regression coefficients is effectively removed. On the basis of screening of the raw data, loop regression computation is carried out by a repeated weighting method for a complex field, influence of strong influential points to the regression coefficients is effectively reduced, and regressive robustness is improved.

The invention discloses a method for detecting harmonic waves of an electric system based on window and interpolated FFT. The method comprises the following steps of obtaining sampling data of detected signals by an analog to digital converter, carrying out an operation of adding Hanning window FFT on the sampling data, searching a peak and an adjacent secondary peak of a spectral line to obtain an interpolation coefficient of a fundamental wave, obtaining the interpolation coefficient of each level of harmonic wave by the interpolation coefficient of the fundamental wave, eliminating the interference of the fundamental wave frequency spectrum to the adjacent harmonic wave frequency spectrum to modify the spectral line of the harmonic wave, and finally obtaining the frequency, the amplitude value and the phase of the fundamental wave and each level of harmonic wave by an interpolation operation. The invention firstly puts forwards that a real spectral line of the harmonic wave can be obtained by eliminating the interference of the fundamental wave frequency spectrum to the adjacent harmonic wave frequency spectrum in the Hanning window FFT spectral line. The scheme of the invention has the advantages of providing the method for detecting the window interpolated FFT harmonic wave with a small calculation amount and high analyzing precision.

Frequencies fx between the measurement harmonic (mth-degree harmonic) and the (m±1)th-degree harmonics are determined from an expression of fx=(fs*m)±{(fs/n)*k)} where n and k are each an integer. Currents of inter-harmonics of the frequencies fx above and below the measurement harmonic are injected into an inject point in a power system in n cycles of the fundamental wave. Voltage at the inject point based on the injected currents and currents at least either upstream or downstream from the inject point are measured. Admittances for the inter-harmonics above and below the measurement harmonic on at least either the upstream or downstream side from the harmonic inject point are calculated from the measurement results. Interpolation processing based on the calculation results is performed, thereby finding and determining an admittance for the measurement harmonic.

The invention discloses a power system harmonious wave compressed signal reconstruction and detection method based on compressed sensing. The power system harmonious wave compressed signal reconstruction and detection method based on compressed sensing comprises the steps that harmonious wave original signals of a power system and a measurement matrix with a binary sparse random measurement matrix serving as a power system harmonious wave data compressed sample are sent to a frequency mixer for compressed sampling in a simulation domain, then A/D conversion is carried out on the simulation signals, and a compressed sampling value is obtained; it is determined that a compressed sensing sparse base is a discrete Fourier transform base; initialization of fundamental wave filtering is carried out; fundamental wave filtering is carried out; the frequency, amplitude and phase of a fundamental component are detected; the fundamental wave constituent in the compressed sampling value is filtered away; parameter initialization is carried out on a spectrum projection gradient method; a sparse vector estimation value of a harmonious wave component is reconstructed through the spectrum projection gradient method; the frequency, amplitude and phase of the harmonious wave component are detected; reconstruction of the harmonious wave original signals of the power system is finished. The power system harmonious wave compressed signal reconstruction and detection method based on compressed sensing overcomes the defect that all existing recovery algorithms do not take the influence of the fundamental wave component in the harmonious wave signals on signal reconstruction into account, so that the recovery effect is not ideal.

The invention discloses a filter device for controlling a harmonic wave of an electric power system. The device comprises a passive filter and an active filter, wherein the passive filter comprises a quintic harmonic wave filter branch circuit, a septic harmonic wave filter branch circuit, and an eleventh harmonic wave filter branch circuit, which are connected in parallel; each harmonic wave filter branch circuit comprises a breaker, a current transformer, a fuse protector, an electric reactor, a capacitor and a bidirectional thyristor which are sequentially connected in series; the active filter comprises a first resistor and a second resistor; the first resistor is connected to a low voltage side of a power grid transformer in series; the second resistor is connected to the other side of the first resistor in parallel; the other end of the second resistor is connected with a base of an insulated grid bipolar transistor; the capacitor is connected between a collector and an emitter of the insulated grid bipolar transistor in parallel; each harmonic wave filter branch circuit of the passive filter and the input end of the active filter are connected to the low voltage side of the transformer in parallel; the output end is connected with the load; and the high voltage side of the transformer is connected with the power grid. The device can remove the harmonic wave, and can achieve the targets of saving energy and reducing emission at the same time.

The invention discloses a measurement and calculation method of harmonic impedance of a power system. A complex least square method is introduced into harmonic impedance calculation of a power system and the phasor real and imaginary parts like a measured voltage and a measured current and the like are used as an organic integrated part to carry out calculation, so that an optimized least square solution is obtained. According to the invention, the data processing process is introduced and original data are screened by using a relative-complex-residual-sorting-based method, so that the influence on a regression coefficient by an abnormal point can be effectively eliminated. On the basis of screening of the original data, circulated regressive calculation is carried out by employing a complex field repeated weighting method, so that the influence on the regression coefficient by the strong influence point can be effectively reduced and the regression robustness is enhanced.

The invention relates to the field of detection of harmonious waves in power systems, in particular to a power system HHT harmonious wave detection method based on improved EMD end point effect. The method comprises the steps of selecting end points and extreme point as reference variables and comparing the relation of the end points and extreme point according to a signal boundary distorting phenomenon occurred in the EMD decomposition course, adopting a mirror image extension method to improve the end point effect, utilizing an improved mirror image method to perform EMD decomposition on the power system harmonious waves so as to obtain all of intrinsic mode function (IMF), utilizing Hilbert conversion to perform decomposition on the power system harmonious waves subjected to the EMD decomposition so as to obtain signal time-frequency characteristics. The power system HHT harmonious wave detection method facilities rapid detection of harmonious wave composition of the power system harmonious waves, accordingly improves the power system harmonious wave recognition capability and is suitable for power systems and relevant departments and used for power system harmonious wave detection.

The invention relates to an empirical mode decomposition-based improved harmonic analysis method. The analysis method includes the following steps that: a central processor sets a sampling period, performs real-time sampling and quantization on the signals of a power system so as to obtain original signals x [t]; empirical mode decomposition is performed on the original signals x [t], so that IMF modal components can be obtained, and HHT transform is performed on the IMF modal components, so that an instantaneous frequency graph can be obtained; frequency differences between the IMF modal components are calculated, and IMF modal components on which mode mixing begins to occur are found out; all IMF modal components before the occurrence of the mode mixing are removed from the original signals x [t]; spectrum analysis is performed on remaining signals, and frequency band filtering is performed on IMF modal components within double frequency; HHT transform is performed on the filtered IMF modal components, so that an instantaneous frequency and amplitude graph can be obtained. With the empirical mode decomposition-based improved harmonic analysis method of the invention adopted, different characteristics of the signals of the power system can be clearly differentiated from the HHT transform graphs, and an effective and rapid analysis mode can be provided for the harmonic analysis of the power system.

The invention relates to a power system harmonic detection device and method. The objective of the invention lies in solving problems that a power system harmonic detection device in the prior art is poor in detection effect, is low in detection precision, and is high in cost. The input end of a voltage transformer and the input end of a current transformer are connected with a power grid. The output ends of the voltage transformer and the current transformer are respectively connected with the input end of a signal conditioning circuit. The output end of the signal conditioning circuit is connected with a DSP controller through a digital-analog conversion module, and the output end of the DSP controller is connected with an ARM processor through a communication module. The device not only obtains an accurate total harmonic distortion rate, but also obtains precise percentages of harmonics at all orders.

The invention provides a self-decision three-phase self-balancing load zero passage switching method which comprises the following steps of data statistics, line impedance calculation, low-voltage tide emulation, load prediction, self-decision control strategy preparation, and three-phase balancing. The self-decision three-phase self-balancing load zero passage switching method is reasonable in design, can effectively reduce the three-phase unbalance degree, can raise the level of safe, stable and economic operation of a whole power grid, can significantly improve the power supply quality of the power grid, can improve a power factor in real time, can effectively manage power system harmonic caused by three-phase unbalance, can well control voltage fluctuation, can prolong the service lifeof power utilization equipment, can improve the power supply quality of the power grid to meet a national standard, can create a good power supply system for industrial and agricultural production and people living, and can exert purposes of energy saving, consumption reduction and great national resource saving.

The invention relates to a harmonic wave responsibility determining method of a power system. The method comprises that a kernel density estimation method is used to calculate the probability density function of a harmonic voltage responsibility sample; a significant sampling Monte Carlo method is used to sample the calculated probability density function; and the mean value and standard deviation of the harmonic voltage responsibility of a harmonic wave source are calculated on the basis of the sampled harmonic voltage responsibility, and the harmonic voltage responsibility of an electric energy quality pollution source is described quantitatively. According to the invention, the harmonic wave responsibility of the harmonic wave source is visually described by utilizing the statistical features, the significant sampling Monte Carlo method is used to sample the calculation result of the harmonic wave responsibility in the calculation process, a series of discontinuous calculation results are extended, restriction of a traditional sampling method is avoided, more extracted sample points are from the area of high probability density on the premise that the sample expectation is not changed, influence of low probability emergent events on the calculation result is effectively avoided, and the accuracy of the calculation result is improved.

The invention belongs to the field of power system harmonic detection and treatment equipment performance test and relates to a full-function electric-energy quality comprehensive test platform. A control system structurally comprises a human-computer interface, a background workstation, an on-site workstation, a video monitoring workstation, a signal conditioning board, a control module and a relay protection device. A data acquisition card and a serial port card are inserted in the on-site workstation. The control module strategically applies IGBT (insulated gate bipolar transistor) controllable rectifying, a CPS (carrier phase shifted)-SPWM (sinusoidal pulse width modulation) multilevel PWM (pulse width modulation) strategy based on the CPS principle is selected, voltage feedforward control is added to an inverting side, and accordingly dynamic performance and stability precision are increased, and tracking error caused by periodic disturbance is eliminated by advanced repetitive learning control so that electric energy quality of an energy-taking power grid is free of influence in test process. By the aid of the test platform, voltage disturbance and current disturbance can be output respectively as well as simultaneously.In addition, the test platform can be converted according to test requirements and is highly practical.

The invention relates to a BPA data based alternating current system harmonic impedance scanning method. The method is characterized by comprising the following steps: (1) establishing each element harmonic impedance model in an electrical power system; (2) reading BPA data, and inputting an appointed frequency range and observation nodes; (3) carrying out node numbering optimization by adopting a semi-dynamic method based on an improved wiring matrix; (4) forming a node admittance matrix line by line according to an optimized numbering sequence; (5) solving a node voltage equation; and (6) changing frequency in the appointed frequency range according to a frequency scanning range, reforming a node admittance matrix, and returning the step (5) to solve the node voltage equation so as to obtain harmonic impedance under different frequencies. Compared with the prior art, the computation speed is obviously increased and is not restricted by node quantity and node voltage level, and the method is widely applied to harmonic impedance computation in the electrical power system.

The invention discloses an electric power system harmonics analysis method based on a multilayered feedforward neural network in the electric power system signal testing technology field. In the invention, an electric power system voltage or current signal is obtained through an optical fiber voltage sensor or an optical fiber current sensor, single hidden layer of the multilayered feedforward neural network is established; an excitation function is a sine and a cosine function and a variable parameter is a harmonic amplitude and an angular frequency; a Hanning window is performed to an obtained electric power system signal; and then discrete fourier transform (DFT) is performed; the sine and cosine component amplitude of each corrected subharmonic and the harmonic angular frequency are taken as an initial weight value of the neural network; an RPROP algorithm training is employed on the basis of the initial weight value; the amplitude and the frequency of the each subharmonic can be acquired according to the trained weight value. By using the method of the invention, accuracy of a calculating result is high and a speed is fast. The harmonic wave analysis accuracy at short sampling time can be greatly raised. A principle is simple and the method is easy to be realized.

The invention discloses a harmonic correlation analysis based electricity system harmonic source recognition device, and belongs to the technical field of electricity system harmonic analysis and evaluation. The harmonic correlation analysis based electricity system harmonic source recognition device comprises K harmonic parameter measuring units, K synchronous sequence generation units, a harmonic-fundamental wave correlation matrix calculation unit, a harmonic-harmonic correlation matrix calculation unit and a harmonic source recognition unit. The harmonic correlation analysis based electricity system harmonic source recognition device has the advantages that data, such as harmonic impedance, harmonic source parameters and nonlinear load parameters, of an electricity system do not need to be known accurately, and the defects of nonsynchronous monitoring of part of outgoing lines in the prior art are overcome; correlation characteristics of each outgoing line and each variable are disclosed, and accordingly, a brand-new road is opened up for harmonic source recognition of transformer substations.

The invention relates to the field of harmonic identification methods, in particular to a harmonic identification method used for harmonic identification in power systems or control systems. The method comprises the following steps: creating response signal non-linear state space model; and extracting state vector estimated value, harmonic amplitude and phase at k moment. The method for harmonic identification based on generalized Kalman filter can obtain accurate information of harmonic component in excitation response signal of simple harmonic wave in a fast and real-time manner, and can be applied to harmonic identification in power systems or control systems conveniently.

The invention discloses a self-adaptation independent component analysis method for harmonic wave impedance estimation, relates to the field of power systems and aims to solve the problems that in theprior art a conventional power system harmonic wave impedance estimation method is low in precision, a novel rapid independent component analysis algorithm is low in convergence performance and source signals cannot be all recovered with an optimal effect. The method comprises the following steps: firstly, sampling a harmonic wave voltage and harmonic wave current at a public coupling point; secondly, carrying out centralization and whitening processing on a harmonic wave voltage sampling value and a harmonic wave current sampling value as known mixed signals; thirdly, with the criterion of negentropy maximization, carrying out iteration so as to obtain a primary separation matrix; finally carrying out self-adaptation selection on nonlinear functions, and carry outing progressivity analysis till an optimal nonlinear function, and calculating a harmonic wave impedance matrix, thereby finally obtaining harmonic wave impedance. By adopting the method, limits of conventional methods are overcome, meanwhile defects of rapid independent component analysis are made up, and the harmonic wave impedance estimation precision can be improved.

The invention discloses a power system harmonic state estimation method based on an automatic differentiation. The automatic differentiation (AD) technology is applied to the power system harmonic state estimation. The method includes that firstly storage allocation is performed for the AD, live variables are described, a network parameter is obtained, a harmonic number is set, and a node admittance matrix of a harmonic is formed; then before iteration, positions and values of invariant elements in a jacobian matrix are stored in a linked list; and the iteration starts, the AD tool is used to calculate variable elements in the jacobian matrix, and simultaneously the invariant elements of the jacobian matrix in the linked list are read to obtain the jacobian matrix required by the harmonic state estimation. According to the power system harmonic state estimation method based on the automatic differentiation, traditional manual differential code writing is replaced by the AD to calculate the jacobian matrix, thereby handwritten code quantity is reduced, development efficiency of programs is increased, truncation error is effectively avoided, computational efficiency of algorithm is improved, and the power system harmonic state estimation method based on the automatic differentiation is convenient to implement on an existing state estimation software.

The invention discloses a method for simulating harmonics of a power system to be connected with an electrified railway. The method comprises the following working steps: (1) establishing an electrical transient analyzer program (ETAP) power system model; (2) utilizing the ETAP model to simulate triple frequency harmonics and multiples of the triple frequency harmonics of the power system to be connected with the electrified railway; (3) utilizing the ETAP model to simulate each frequency harmonic of the power system to be connected with the electrified railway except for the triple frequency harmonics and the multiples of the triple frequency harmonics; and (4) utilizing the ETAP model to simulate each frequency harmonic of the power system to be connected with the electrified railway. According to the method, the complexity of large-scale power system modeling is simplified, the difficulty of load flow calculation and debugging is overcome and the simulation and the research of the harmonics connected with the electrified railway are realized quickly and effectively. The method can be used for evaluating the impact on power quality of the power system before a power supply system is connected with the electrified railway, thereby guiding planning and design of the power system.

The present invention discloses a power system harmonic current estimation method for wind power integration. According to the method, firstly, the collected historical harmonic current data of each bus are subjected to wavelet decomposition and filtering, and then the high frequency components and the low frequency components of the data are obtained. Secondly, a harmonic current estimation measurement model and a state transition model are established. Finally, the harmonic current is estimated by adopting the variable-parameter kalman filtering method. According to the technical scheme of the invention, low frequency components, which embody the fluctuation rule of harmonic waves, are adopted as the preliminary estimation for the state of harmonic waves at the next moment. Meanwhile, a state transition matrix is estimated by utilizing the low frequency components. The daily fluctuation regularity of the injected harmonic current for an ordinary harmonic source load and a wind power harmonic source load is fully considered, and the estimation accuracy of the harmonic current is improved. High frequency components, which embody the randomness of the harmonic current, are adopted as the system noise and are used for estimating a system noise covariance matrix. Therefore, the complex noise parameter adjustment process of the kalman filtering method is avoided. The work load is reduced and the adaptability in different network structures is improved.