383 results about "Harmonic impedance" patented technology

The invention dsiclsoes a microgrid system with an asymmetric non-linear load and a power balancing control method. The system comprises a plurality of DG units connected in parallel and line impedors connected with all DG units. The line impedors are connected to a microgrid bus by PCC points. A three-phase balancing resistive load, an asymmetric linear load, and a diode rectifier non-linear load of a load unit are connected to the microgrid bus by PCC points. A measurement module for measuring voltage fundamental wave positive sequence and negative sequence components and harmonic wave components of the PCC points is also connected to the microgrid bus. The microgrid bus is connected with a 10-kV main power grid by a static switch and a transformer successively. According to the invention, reactive and harmonic power balancing of the microgrid is realized by using a selective virtual impedance based on the virtual fundamental positive and negative sequence impedance and the virtual variable harmonic impedance; a harmonic and unbalancing voltage compensation controller enables equal division of an unbalanced power and a harmonic power to be realized; and a problem of unbalancing of the harmonic wave and the voltage of the microgrid can be solved.

Disclosed is a Doherty amplifier which includes a carrier amplifier for always performing a signal amplification operation regardless of a level of an input signal, a peaking amplifier for performing an amplification operation, starting from a high power output where a level of an input signal is equal to or greater than a predetermined level, an output combination circuit for combining and outputting outputs of the carrier amplifier and the peaking amplifier, and an input division circuit for dividing an input signal into the carrier amplifier and the peaking amplifier, the Doherty amplifier including a carrier amplifier output harmonic impedance tuning network which is installed at a rear end of the carrier amplifier so as to tune an output harmonic impedance of the carrier amplifier, and a peaking amplifier output harmonic impedance tuning network which is installed at a rear end of the peaking amplifier so as to tune an output harmonic impedance of the peaking amplifier.

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 is suitable for the field of radio frequency communication, and provides a double-stage inversing D-class power amplifying circuit and a radio frequency power amplifier. The circuit comprises an input passive component connected with a block condenser, a positive and negative double-way driving-stage F-class amplifier, a positive and negative double-way amplifying-stage inversing F-class amplifier and an output passive component, wherein the two input ends of the positive and negative double-way driving-stage F-class amplifier are connected with the two output ends of the input passive component through two block coupling condensers, the two input ends of the positive and negative double-way amplifying-stage inversing F-class amplifier are connected with the two output ends of the positive and negative double-way driving-stage F-class amplifier through two condensers, and the two input ends of the output passive component are connected with the two output ends of the positive and negative double-way amplifying-stage inversing F-class amplifier through the two condensers. By utilizing an F-class driving inversing F-class push-pull structure, according to the harmonic shaping technology, the efficiency, the power and the gain of the power amplifier are improved, the independent control from a fundamental wave to a triple frequency harmonic impedance is achieved, the design difficulty is lowered, and the tedious debugging work in the later period is lowered. In addition, due to the positive and negative double-way structural design, the power and the gain are further improved.

The invention relates to a method and a device for measuring harmonic impedance. Aiming at the main error source in an 'incremental method' of the method for measuring the harmonic impedance, namely the problem of the synchronization of frequency deviation and two different time signal phase angles, the invention discloses a 'bisynchronous incremental method', and develops a corresponding testing instrument, wherein the first synchronization is that a reference phase is synchronized with the system cycle to solve the drifting problem of the reference phase; and the second synchronization is that the sampling frequency is synchronized with the system frequency by tracking the changes of the system frequency by a hardware phase lock circuit and generating the sampling frequency by the phase lock circuit. The device for measuring the harmonic impedance comprises a synchronous circuit of the sampling frequency and the system frequency and a synchronous circuit of the phase and the system cycle. The 'bisynchronous incremental method' solves the error problems caused by benchmark reference phases, system frequency fluctuations and the like in the 'incremental method'; the device has a simple principle and is easy to implement; and the method and the device reach the engineering application level and solve the problem of measuring the harmonic impedance in the generation of electricity.

The invention discloses a harmonic contribution calculating method applicable to a background harmonic voltage change. The harmonic contribution calculating method comprises the steps that under the condition of a plurality of harmonic sources, the system harmonic impedance is estimated through a leading fluctuation quantity method; clustering processing is conducted on background harmonic voltage data through a mean shift algorithm according to the change conditions of the background harmonic voltage, and the background harmonic voltage data are divided into different data segments according to background harmonic voltage values; harmonic contributions of the data segments are calculated through a partial least square method, weighted summation is conducted, and therefore the harmonic contribution in a focused time period can be obtained. The harmonic contribution calculating method improves accuracy of harmonic contribution calculation, and can effectively eliminate the influence of the background harmonic voltage change on harmonic contribution calculation.

The invention provides a method for calculating harmonic wave impedance of an alternating current system for direct current transmission. The method includes the following steps that a node admittance matrix is formed according to a harmonic wave model of a transmission line, a transformer, a generator, a load and a parallel capacitor; nodes to be calculated are placed at the bottom line of the admittance matrix, the current value at the bottom line is set to be 1, and the current values at other lines are set to be 0; node optimizing numbering is conducted on the first n-1 nodes; the node admittance matrix is stored through a sparse technology; the node admittance matrix is solved, and the back substitution does not need to be conducted; a plurality of input files are simultaneously calculated through a parallel calculation method; statistic analysis is conducted according to the batch processing calculation result. According to the method, specific to the characteristic that multiple times of scanning needs to be conducted for calculating the harmonic wave impedance, the improved node optimizing numbering technology and the improved sparse technology are adopted, and therefore the workload for calculating the harmonic wave impedance is reduced, the calculating speed is greatly increased, burdens of operators are relieved, and precious time can be saved.

The invention discloses a method for computing harmonic impedance of a system based on maximum likelihood estimation theory. The method is characterized by comprising the following steps: collecting bus voltage instantaneous value of common coupling point and current instantaneous value of user access system, and establishing a relation between harmonic voltage phasor and harmonic current phasor; on the basis of defining a complex covariance, deriving to obtain a probability density function of unary complex normal distribution so as to obtain a maximum likelihood estimation function; establishing the maximum likelihood estimation theory of complex field estimated by the harmonic impedance of system; utilizing an extreme value theory to solve the maximum likelihood estimation function so as to obtain the estimated value of harmonic impedance of the system finally. The method has the beneficial effects that the method for computing harmonic impedance of the system based on maximum likelihood estimation theory is capable of relatively accurately computing equivalent harmonic impedance of the system and has important meanings for further solving the problem of harmonic pollution and improving the management level of electric energy quality.

The invention relates to a harmonic contribution division method and a harmonic contribution division system. The harmonic contribution division method comprises the following steps of acquiring harmonic voltage data of a bus and harmonic current data of a harmonic source to be calculated on a feeder line; calculating background harmonic impedance by using a leading fluctuation quantity method according to the harmonic voltage data and the harmonic current data; and dividing harmonic contributions of the harmonic source to be calculated by using a quantile regression method according to the harmonic voltage data, the harmonic current data and the background harmonic impedance. The background harmonic impedance is estimated by the leading fluctuation quantity method, fluctuation quantity with a leading function is screened out to calculate the background harmonic impedance, influences of background harmonic and measurement noise fluctuation on a background harmonic impedance estimation result are restrained effectively, and the background harmonic impedance is calculated accurately; and the background harmonic current is calculated according to the background harmonic impedance, and quantile regression is performed to obtain the harmonic contributions of the harmonic source. Calculation deviation caused by background harmonic fluctuation can be reduced, division accuracy is improved, and the stability and the data utilization rate are high.

The invention discloses a method for solving the equivalent impedance frequency characteristic of an HVDC transmission system converter under various operating conditions and failure conditions, whichcomprises the following steps: according to the fundamental component of voltage between phases of converting buses and the DC component of direct current, and a trigger angle instruction of a DC control system, calculating the actual trigger angle of each converting valve and the delay angle of flow of the converting valve in the converter, and the actual phase-change angle when two phases are converted; then calculating a three-phase voltage switching function and a three-phase current switching function; and by the subharmonic components of the three-phase voltage switching function and the three-phase current switching function, and the equivalent harmonic impedance of an AC network and a DC network, calculating the equivalent harmonic impedances at the AC side and the DC side of theconverter. The method can realize the calculation of the equivalent harmonic impedances at the AC side and the DC side of the converter under various AC operating conditions and failure conditions, reduce the calculation amount and meet the demand on precision in engineering application.

The invention discloses a fluctuation quantity method-based user side harmonic emission level practicality estimation method, belongs to the field of power quality harmonic treatment, is used for dividing rights and liabilities of harmonic pollution on a power supply side and an electricity side and belongs to a theoretical method practicality technology. The invention provides a complete processfor estimating the user side harmonic emission level by employing a fluctuation quantity method, provides a method for quantizing deviation between a power supply side harmonic impedance amplitude estimated value and an actual value, provides power supply side harmonic impedance amplitude estimated value accuracy for engineering, and easily and quantitatively judges whether the estimated value meets the requirement on engineering accuracy. In the method, various problems which possibly exist in actual engineering are considered theoretically. The conception of the time-varying dynamic phasor-based fluctuation quantity method is stated, the conventional harmonic impedance estimated value algorithm is improved, the least squares fitting algorithm which is wider in applicability and higher in accuracy is provided to estimate power supply side harmonic impedance; therefore, a practical flow more accords with actual operating conditions of a power system.

An alternating current electrified railway traction network impedance frequency characteristic testing device is composed of a step-down transformer TP, a harmonic source HS, a monitoring device MC, a voltage transducer TV and a current transducer TA. The monitoring device MC controls that the harmonic source HS sends harmonic current and injects a primary side winding of the step-down transformer TP into a traction network. The voltage transducer TV and the current transducer TA respectively detects harmonic voltage between a contact network T and a steel rail G and the harmonic current injected into the traction network, and the monitoring device MC receives output signals of the voltage transducer TV and the current transducer TA and finishes harmonic impedance calculation. Under the situation that the contact network is electrified, an impedance frequency characteristic of the traction network can be obtained by adjusting the frequency and amplitude of the current sent by the harmonic source, and further the harmonic frequency is obtained. The alternating current electrified railway traction network impedance frequency characteristic testing device can be used for newly-constructed electrified railway joint debugging integration test and can be also used for providing technical support for solving the harmonic vibration problem and guaranteeing power supply safety of existing lines.

The invention discloses a micro-grid harmonic impedance measuring method based on three-phase symmetrical square wave current injection. The method comprises the following steps: injecting three-phase symmetrical square wave current ih into a certain node of a micro-grid and measuring the voltage disturbance caused by injection; sampling the square wave current ih and the voltage disturbance delta uh, wherein the sampling ratio and the sampling point number meet the requirement of a base-2FFT algorithm; and performing quick Fourier transformation on the sampled square wave current ih and the voltage disturbance delta uh. The harmonic impedance of the micro-grid is measured by injecting the three-phase square wave current into the certain node of the micro-grid. In a micro-grid simulation model based on PSCAD, the harmonic impedance of the system under a droop control mode is measured by the method; and according to the simulation result, the measuring value basically coincides with the theoretical calculation value, so that the method is correct and practical.

The invention discloses a distribution method based on waveform matching for harmonic voltage responsibility. The distribution method comprises the steps of: step 10) acquiring harmonic test data, and forming a harmonic data sequence; step 20) setting basic matching parameters; step 30) calculating an Euclidean distance, wherein normalization processing is performed on the harmonic data sequence which is formed in the step 10) according to a sequence of subsequences based on the basic matching parameters set in the step 20) to obtain harmonic sample data, and the Euclidean distance between a harmonic voltage and a harmonic current in the harmonic sample data is calculated; step 40) screening the subsequences, wherein similarity of each subsequence is calculated, and the subsequence with the similarity not less than a set value is screened out; step 50) and distributing harmonic responsibility, wherein system-side equivalent harmonic impedances of the screened subsequences is estimated by adopting a least square method, and a mean value of the equivalent harmonic impedances is utilized for calculating the harmonic voltage responsibility. The distribution method can quantify harmonic pollution liability of a feeder by utilizing harmonic amplitude data, and is suitable for engineering practice.

The invention provides a quantitative analysis method of a harmonic voltage transmission level of a nonlinear load of a user terminal and a corresponding device. The method comprises the steps: sampling voltage and current in a common coupling point between a power supply terminal and the user terminal; obtaining several harmonic voltage phasors and current phasors according to sampling data; judging whether the nonlinear load of the user terminal is a main harmonic source or not; computing the harmonic impedance of the power supply terminal if the nonlinear load of the user terminal is the main harmonic source; and computing the harmonic voltage transmission level of the nonlinear load of the user terminal in a time interval according to the harmonic impedance of the power supply terminal and the current phasors in the common coupling point. By applying the method, the harmonic voltage transmission level of the nonlinear load of the user terminal can be easily and quantitively analyzed.

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 a grid high-frequency impedance remodeling device for suppressing distributed generation resonance. The remodeling device is composed of a power grid-connected converter and aresonant impedance controller. The resonant impedance controller consists of a resonant detection module and a resonant current tracking module. The resonant detection module detects the voltage upccof a PCC point by a voltage sensor; predetermined circuit processing is carried out on the voltage upcc to obtain resonant voltage components upccr<+> and upccr< > and a resonant frequency omega r; and predetermined circuit processing is carried out on the resonant voltage components upccr<+> and upccr< >, the resonant frequency omega r, the voltage upcc of the PCC point, and a direct-current voltage Udc by the resonant current tracking module to obtain a PWM pulse signal for controlling connection or disconnection of a switching tube of a power grid-connected converter. According to the invention, the grid high-frequency impedance remodeling device is installed at the PCC point and detects the resonant voltage components of the PCC point; the resonant impedance controller including equivalent damping resistance information is used for obtaining a current instruction outputted by the converter; the converter is controlled to track the instruction value; and a virtual variable harmonicimpedance is generated to realize grid harmonic suppression.

The invention relates to a reconfigurable radio frequency and microwave power amplifier. The reconfigurable radio frequency and microwave power amplifier comprises an input radio frequency switch, anadjustable input matching network, a power amplifier stage, an adjustable output matching network and an output radio frequency switch which are connected in turn, and an adjustable harmonic impedancecontrol network and a bias and control circuit; and the adjustable input matching network and the adjustable output matching network respectively comprise at least one LC network with a fundamental wave impedance conversion function, wherein the LC network comprises at least one reconfigurable device, and the reconfigurable device is connected with a passive device in the LC network in parallel.According to the reconfigurable radio frequency and microwave power amplifier provided by the invention, the reconfigurable harmonic impedance control network and the fundamental wave impedance matching network are realized through the adjustable input matching network, the adjustable harmonic impedance control network and the adjustable output matching network; and when a power amplifier works indifferent bands of a linear power amplifier mode, a load impedance network can be reconfigured in real time, which satisfies the fundamental wave impedance and harmonic load required by each frequency band.

The invention discloses a multi-harmonic-source harmonic contribution quantitative analysis method based on a total-least square method. The multi-harmonic-source harmonic contribution quantitative analysis method includes: selecting harmonic voltage as the index for evaluating harmonic contribution, and determining the joint action of the harmonic source of each node; sectioning measured data according to time, and calculating the harmonic contribution in each time section according to the projection of the harmonic voltage of one harmonic source at one node on the total harmonic voltage at the node; using the total-least square method to solve harmonic impedance and the harmonic voltage, namely background harmonic voltage, of other harmonic sources at the node, and using a singular value decomposition method to obtain the solution of the total-least square method to obtain the quantitative data of each harmonic source at each node at each harmonic time. The multi-harmonic-source harmonic contribution quantitative analysis method has the advantages that the total-least square method is applied to the harmonic quantitative analysis field, the defect that a traditional method only considers variable harmonic voltage measuring errors and does not consider the independent variable harmonic current measuring errors is overcome, and obtained results are accurate.

The invention relates to a harmonic current estimation method under the condition of unknown harmonic impedance, and the method comprises the steps: taking a harmonic voltage as a measurement quantity and taking a harmonic current as a state quantity according to the statistic independence and super-Gaussian distribution characteristics of a harmonic current quick fluctuation quantity, and building a harmonic state estimation model comprising measurement noise; enabling the noise and impedance parameters in an ICA model to serve as unknown variables, enabling the harmonic current to serve as a hidden variable, and obtaining a harmonic current optimal solution which cannot be affected by noise through employing the variational Bayesian learning capability for unknown variables; neglecting linear load admittance according to the characteristic that the linear load admittance is far less than system side admittance, eliciting a harmonic current amplitude proportion coefficient, and determining the current amplitude. Compared with the prior art, the method can effectively eliminate the uncertainty of an independent component analysis algorithm and restores the amplitude of the harmonic current with no need of harmonic impedance parameters, obtains an estimated harmonic current, can effectively reduce the impact on the estimation result from measurement noise, and is stronger in robustness.

The present invention belongs to the field of harmonic impedance calculation method design and more particularly relates to a power system harmonic impedance calculation method. The method is characterized in that firstly, the voltage and current measured at a PCC are subjected to Fourier decomposition, the effective values of voltage and current obtained after the decomposition and an initial phase are constructed into a harmonic voltage vector sequence and a harmonic current vector sequence under a target frequency of a common connection point; then a regression equation is established by the voltage and current harmonic vector sequences; and finally a system harmonic impedance regression coefficient is solved by the mixed overall least square method, and the value of harmonic impedance is obtained. The invention provides the system harmonic impedance calculation method based on a mixed overall least square method, independent variable and dependent variable errors are completely considered, the partial error of an overall minimum least-square coefficient matrix is considered closely, a regression coefficient estimation error can be effectively eliminated or reduced, and the system harmonic impedance solution accuracy is improved.

The invention is suitable for the field of radio frequency communication and provides a J type power amplification circuit based on parasitic compensation and a radio frequency power amplifier. The circuit comprises a transistor, a parasitic circuit, a harmonic parasitic compensation unit, a harmonic impedance control unit and a fundamental wave impedance control unit, wherein the input end of the harmonic parasitic compensation unit is connected with the power signal output end of the transistor; the input end of the harmonic impedance control unit is connected with the output end of the harmonic parasitic compensation unit; the input end of the fundamental wave impedance control unit is connected with the output end of the harmonic impedance control unit, and the output end of the fundamental wave impedance control unit is connected with a load through a capacitor. According to the J type power amplification circuit based on parasitic compensation, a harmonic parasitic compensation network is utilized to compensate on harmonic impedance of the transistor of the power amplifier, so that the accurate control of fundamental wave impedance, second harmonic impedance and third harmonic impedance is achieved, the energy loss of the transistor is reduced, the efficiency and linearity of the power amplifier are improved; through independent design of the second harmonic impedance and the third harmonic impedance, each harmonic impedance control circuit does not affect each other, the optimized debugging at a later period is not needed, and the design complexity is reduced.

The invention discloses a multi-frequency-band power amplifier which comprises a power amplifying unit for amplifying signals of multi-frequency-band and a harmonic suppression circuit; the harmonic suppression circuit is connected with the output route of the power amplifying unit when the power amplifying unit amplifies the signal of one frequency band; and when the power amplifying unit amplifies the signal of the other frequency band, the harmonic suppression circuit is disconnected with the output route of the power amplifying unit by the harmonic of the signal of the frequency band which is suppressed and amplified by the harmonic suppression circuit. Thus, the effect of an equal efficiency power amplifier similar to F power amplifiers is realized by the harmonic suppression circuit, i.e. the output power and the efficiency are changed through changing the harmonic impedance, so that the output filter wave, the power and the efficiency of the power amplifier are improved under the premise of not disturbing the normal signal of the other frequency band.

The invention discloses a novel harmonic emission level assessment method. Harmonic equivalent circuits of a system and a user at a point of common coupling (PCC) are analyzed to obtain a relational expression between the harmonic impedance of the system and the user and the voltage and current at the PCC; a certain mathematical operation is conducted on voltage signals and current signals, wherein the voltage signals and the current signals are collected at the PCC; h subharmonic voltage signals and current signals are extracted; on the basis of data envelopment analysis of the signals, partial least square regression molding is conducted to obtain the estimated result of the harmonic impedance; lastly, the regression result is utilized for assessing the harmonic emission level of the user. According to the novel harmonic emission level assessment method, the data envelopment analysis is adopted for optimizing harmonic voltage and current values obtained through measurement at the PCC, invalid data caused by system operation fluctuation or a measuring instrument are eliminated, the defect that partial least square regression obtains a wrong model according to wrong data is overcome, the accuracy of the estimated result is greatly improved, and a basis is provided for duty allocation between the system and the user with respect to the power quality contamination status.

The present invention relates to a harmonic source positioning and harmonic responsibility division method applied to an active distribution network. The main technical feature is that the method comprises a step of collecting the voltage and current of a common coupling point, a step of drawing the time-domain curve of an equivalent impedance and obtaining a harmonic source location, a step of obtaining the data needed by a harmonic impedance, and a step of calculating the harmonic mutual impedance between a concerned bus and each harmonic source and dividing harmonic responsibilities. The design of the method is reasonable, through establishing a load time-domain equivalent model, by using the physical relation of the voltage and current on a common coupling point, a parameter identification method is used to position the harmonic source in the active distribution network, through analyzing the bus harmonic voltage acted by all harmonic sources in the active distribution network and calculating the harmonic mutual impedance between the bus and the node where the harmonic source is to recognize the contribution of each harmonic source, and thereby a harmonic contribution standard measure is used to divide the responsibility of each harmonic source.

The invention discloses a subsynchronous oscillation source location method and apparatus. The method comprises the following steps: when subsynchronouos oscillation of a regional power grid is detected, carrying out signal processing for a connection wire between the regional power grid and a main network as well as various power supply wires in the regional power grid, filtering components of interharmonics voltage and current on the connection wire between the regional power grid and the main network, calculating interharmonics impedance, filtering fluctuating power in each circuit power, judging whether an oscillation source exists in the regional power grid or not according to the interharmonics impedance of the connection wire between the regional power grid and the main network, and if the oscillation source exists, determining a specific oscillation source according to the coherence of a variation track of the fluctuating power of each power supply wire in the regional power grid and a variation track of the fluctuating power of the connection wire. The oscillation source in the regional power grid can be located by only acquiring the local information of a load-center substation without depending on the wide area information of different transformation substations and a communication network, and the construction of practical engineering is facilitated.

The invention discloses a device and a method for the harmonic impedance measurement of a micro-grid. The device comprises a harmonic current source injection device, a harmonic voltage and harmonic current detection device, a data acquisition device and an upper computer, wherein the harmonic current source injection device is used for injecting harmonic current into the grid; the harmonic voltage and harmonic current detection circuit is used for detecting the magnetic harmonic voltage and harmonic current in the grid before and after the harmonic current is injected into the micro-grid; the data acquisition device is used for sampling a signal detected by the harmonic voltage and harmonic current detection circuit, and transmitting data to the upper computer; the upper computer is used for processing the sampled signal, calculating the variations of the harmonic voltage and the harmonic current, and calculating the harmonic impedance of each part of the micro-grid. According to device and the method, harmonic current of which the amplitude, frequency, phase and waveform can be controlled can be injected into the grid through the harmonic current source injection device, so that the harmonic impedance measurement accuracy of the grid is improved.

A method for determining harmonic voltage comprises the steps of obtaining the fundamental wave voltage and the injection electric quantity of each of the nodes, and determining positive-sequence, negative-sequence and zero-sequence current of each of the nodes; according to the fundamental wave voltage and positive-sequence, negative-sequence and zero-sequence current of each of the nodes, determining positive-sequence, negative-sequence and zero-sequence admittance matrixes of each of the nodes; numbering each of the nodes with a node numbering method, and conducting factorization on positive-sequence, negative-sequence and zero-sequence admittance matrixes with an LU decomposition according to the numbering sequence; and using harmonic power flow models to determine harmonic impedance of each of the branches, determining positive-sequence harmonic voltage, negative-sequence harmonic voltage and zero-sequence harmonic voltage of each of the nodes according to the harmonic impedance of branches and positive-sequence, negative-sequence and zero-sequence admittance matrixes after factorization, and determining the harmonic voltage of each of the node according to the positive-sequence harmonic voltage, the negative-sequence harmonic voltage and the zero-sequence harmonic voltage. The invention also provides a corresponding system. By the aid of the method and the system, the calculation precision can be improved, and the calculation can be simplified.