41 results about "Finite difference coefficient" patented technology

The invention provides a nonlinear optimization based time-space domain staggered grid finite difference method and device. The method includes: determining finite difference coefficients; optimizing the finite difference coefficients on the basis of time-space domain dispersion relation and a nonlinear inversion algorithm; utilizing the optimized finite difference coefficients to perform elastic wave forward modeling. By the method and device, the technical problems of high middle-high frequency dispersion and low simulation precision caused by the fact that a finite difference method of taylor series expansion and space domain dispersion relation is utilized to acquire the finite difference coefficients so as to perform elastic wave forward modeling are solved, dispersion of middle and high frequency is achieved, and technical effect of simulation precision is improved.

The invention provides an elastic migration seismic wave field construction method and an elastic migration seismic wave field construction device. The method includes computing a finite difference coefficient of extended compact staggered grids according to an elastic wave velocity stress equation; computing a finite difference operator matrix of the extended compact staggered grids; constructing forward direction extrapolation operator of a seismic source wave field, and a reverse-time extrapolation operator of a detection wave field; achieving forward direction extrapolation of a seismic wave field to obtain the seismic source wave field according to the forward direction extrapolation operator of the seismic source wave field, a preset medium model and a preset seismic source function; and achieving reverse-time extrapolation of the seismic wave field to obtain the detection wave field according to the reverse-time extrapolation operator of the detection wave field, a preset medium model and preset multi-component seismic data. Compared with an existing method for constructing an elastic deflection seismic wave field by utilization of a conventional finite difference method and a compact difference method, the number of difference base frame grid points is reduced under the condition of same difference orders, the construction precision of a complex medium wave field can be effectively improved, and therefore the imaging precision of reverse-time migration is improved.

The invention belongs to the field of oil-gas exploration seismic data processing and provides a combined imaging method based on various seismic data, such as ground seismic data, cross-well seismicdata and borehole seismic data. The important content of the invention aims to realize the high-resolution and high-fidelity imaging of seismic data, and particularly relates to a full-wave field VSP/RVSP seismic data-based inverse-time migration method. According to the method, based on seismic data collected by a VSP/RVSP observation system, an optimized optimal finite difference coefficient isapplied to a finite difference algorithm of a variable grid. After that, the wave field extension is carried out, and simulated seismic source shot records received by all boundaries are obtained by utilizing an extended seismic source wave field. The seismic source wave field is reconstructed by utilizing the seismic source shot records. Meanwhile, the related imaging is carried out on a detectedwave field after the reverse extension process. The preset wave field separation of a full-wave equation is not required, so that the wave field calculation is more reasonable and more accurate.

The invention relates to an unconditionally stable finite difference seismic wave field continuation method based on a staggered grid Lowrank operator. The method comprises the steps that a first-order speed-stress equation Fourier integral solution is utilized for constructing the Lowrank operator on a staggered grid; an attenuation function is utilized for carrying out attenuation constraint on the staggered grid Lowrank operator; the weighted least square method is utilized for calculating a finite difference coefficient; the obtained finite difference coefficient is utilized for achieving unconditionally stable finite difference seismic wave field continuation. On the basis of the Lowrank decomposition approximate wave number-spatial domain operator, the computationally-stable and high-precision optimized finite difference coefficient is obtained through the attenuation constraint and the weighted least square method, and unconditionally stable finite difference seismic wave field continuation can be achieved through the constructed finite difference computational format.

The invention discloses an optimum design method of a finite difference template of a non-equiangular long-grid wave equation. The method comprises the following steps: according to a time sampling interval and a spatial sampling interval, mesh subdivision is executed to the simulating region of an actual geologic model; according to the maximum appointed permissible error and the wave number range, the corresponding operator lengths of different acoustic velocities are calculated; based on the finite difference method of the least square optimization time space domain and the corresponding operator length, the optimized finite difference coefficient of the grid is acquired; the acquired optimized finite difference coefficient is brought into the wave equation with a difference scheme to perform forward modeling of the wave equation. According to the method, the finite difference method of the time space domain only applied to square and cube grids is expanded into the rectangular or rectangular parallelepiped grids, thus a special simulation precision requirement and a requirement for saving a calculated amount are met in actual production.

The invention discloses an implicit staggered-grid finite difference elastic wave numerical simulation method and device. The method comprises the steps that a dispersion relation expression is obtained based on an implicit staggered-grid finite difference scheme and a plane wave theoretical formula; (M+1) discrete points are evenly taken within the value range of beta in the dispersion relation expression, and the left and right sides of the dispersion relation expression are set to be equal on the discrete points so that a linear algebraic equation set is obtained; the linear algebraic equation set is solved so that the implicit staggered-grid finite difference coefficient am and constant b are obtained; an elastic wave equation is solved based on the implicit staggered-grid finite difference coefficient am, the constant b and the implicit staggered-grid finite difference format; and a wave field diagram is generated according to the solving result and wave field analysis is performed according to the wave field diagram. The solving error of the elastic wave equation can be reduced and the numerical solution accuracy can be enhanced so that a more accurate wave field stimulation record can be obtained. When the same calculation error is constrained, calculation time can be reduced and calculation efficiency can be enhanced.

The invention discloses a small-scale big model forward modeling method based on a wave equation, and relates to the technical field of earthquake exploration. The method includes the steps of (1) absorbing boundary key parameter calculation, (2) cross-scale model design, (3) model discretization and observation system parameter design, (4) optimization and calculation of a finite difference coefficient, (5) small-scale model area forward modeling, (6) large-scale boundary area forward modeling, (7) optimization and calculation of a finite difference coefficient of a transition area, (8) forward modeling based on time step non-linear interpolation, and (9) output of wave equation forward modeling simulation records. By means of the method, a large-scale gird is introduced into an absorbing boundary, so that waste of memory resources is effectively avoided, and calculation efficiency of small-scale big model forward modeling simulation is improved.

The invention provides an energy storage inverter virtual synchronization method and system for adaptive optimization of power grid strength. The method includes data acquisition, power calculation, output calculation of a virtual speed governor, output calculation of a rotor mechanical equation, power grid impedance calculation, damping value spline interpolation fitting and parameter updating. Improvement is made on the virtual damping link. By introducing differential into the virtual damping link, the virtual damping has no effect on the virtual difference coefficient, and the steady stateerror of the primary frequency modulation of a virtual synchronous machine is eliminated. Meanwhile, a first-order inertia link is introduced to improve the stability of the system. Adaptive parameter optimization control is carried out on the virtual damping link. The impedance of the power grid is detected online by harmonic injection, and the parameters of the damping link are adjusted onlineaccording to the detected impedance of the power grid and an adaptive formula, so that the virtual synchronous machine can have better response characteristic before and after the change of power gridstrength.

The invention discloses a time high-order precision staggered mesh finite difference method for variable density acoustic wave equations, comprising: designing a new difference template; using the newdifference template to perform staggered mesh finite difference numerical dispersing on the variable density acoustic wave equations; deducing a frequency dispersion relationship of the variable density acoustic wave equations under the new difference template; using Taylor series expansion or an optimal method to solve a new finite difference coefficient; introducing the new difference coefficient into corresponding discrete equations so as to perform numerical simulation on the variable density acoustic wave equations; analyzing precision and stability of the novel difference method. The time high-order precision staggered mesh finite difference method for variable density acoustic wave equations has the advantages that precise temporal (2M) order and time 10-order simulation precisionare provided, calculating efficiency can be improved by extending time step length; zero distortion of waveform in remote simulation can be better guaranteed.

The invention discloses an elastic reverse time migration method and system based on lowrank finite difference. The method comprises the following steps that: a lowrank finite difference coefficient is constructed; forward and reverse elastic wave field continuation is achieved on the basis of the discretization wave equation of the constructed lowrank finite difference coefficient; and PP and PSimaging profiles are obtained through the obtained forward and reverse elastic wave fields and scalar product imaging conditions. According to the method and system of the invention, the finite difference operator considering time and space is constructed by using a plane wave theory and a lowrank decomposition method and can meet the requirements of high-precision elastic wave field continuationin time and space directions; multi-component seismic data are fully utilized, longitudinal waves and transverse waves of vectors can be obtained in a continuation process, and therefore, the vector characteristics of an underground wave field are kept; the problems of the crosstalk of different wave modes and the polarity correction of converted waves in conventional elastic reverse time migration are avoided in an imaging process; and the imaging precision of elastic reverse time migration is improved.

The invention provides a tuning method for a difference coefficient of a synchronous generator excitation system. The method comprises the following steps: firstly, clearly distinguishing the number of regional central points, an operating voltage of each central point in each period, the number of generator nodes, active output power of each generator, and a load value of power supply by each generator; then, calculating a standard deviation index of a central point voltage, measuring voltage fluctuation, calculating an average active power grid loss rate index, and considering the operationeconomy of the system; and finally, establishing a multi-objective optimization model of the difference coefficient of the synchronous generator excitation system, taking the minimum of the standard deviation of the central point voltage and the average active power grid loss rate as an objective, and calculating an optimal difference coefficient by considering constraint conditions such as powerflow constraint, control variable constraint and safety constraint. According to the tuning method for the difference coefficient of the synchronous generator excitation system, grid voltage can be effectively improved and power grid loss can be effectively reduced.

The invention provides a seismic vector wave field numerical simulation method and system based on a hybrid swarm intelligence algorithm, computer equipment and a computer readable storage medium, andrelates to the technical field of seismic exploration. The method comprises: constructing an improved PSO-BFO hybrid swarm intelligence algorithm; using improved PSO-BFO hybrid swarm intelligence algorithm for carrying out optimization solution on the objective function containing the finite difference coefficient to obtain an optimized finite difference coefficient; and carrying out numerical simulation on the seismic vector wave field according to a finite difference operator formed by the optimized finite difference coefficient. Improved PSO-BFO hybrid swarm intelligence algorithm is designed in the invention,the objective function containing the finite difference coefficient is optimized and solved, the optimized finite difference coefficient is obtained, then the finite difference operator composed of the finite difference coefficient is used for carrying out seismic vector wave field numerical simulation, and the seismic vector wave field numerical simulation precision and efficiency are improved.

The invention discloses a magnetic sensor detection method and a magnetic sensor detection system. The method comprises the following steps: acquiring the background data of all the channels of a magnetic sensor; determining that the maximum value of the background data of every channel is smaller than a preset first threshold and the minimum value is greater than a preset second threshold, or determining that the number of random noise points in the background data of every channel is smaller than a preset number; determining that the difference parameter of the background data of the channels is smaller than a preset parameter; determining that the average difference coefficient of the background data of the channels is smaller than a preset coefficient; and detecting that the magnetic sensor is qualified. According to the invention, the background data of all the channels of the magnetic sensor is acquired, and whether the magnetic sensor is qualified or not can be detected according to the maximum values, minimum values, random noise points, difference parameter and average difference coefficient of the background data of all the channels.

The invention relates to a time domain acoustic wave equation explicit finite difference seismic response simulation method. The method includes the following steps that: 1) the initial value and allowable maximum approximation error xi of spatial difference operator length 2M+1 are set; 2) on the basis of space-wave number domain function approximation-based spatial finite difference coefficient solving method, the difference coefficient and wave number domain error function value of an explicit finite difference formula which is built based on K-space operator compensation numerical value simulation error are solved according to the acoustic wave speed of a target region; 3) if the wave number domain error function value is larger than the allowable maximum approximation error xi, 1 is added to the value of M, and the method returns to step 2), if the wave number domain error function value is smaller than the allowable maximum approximation error xi, and M is larger than 1, 1 is subtracted from the value of M, and the method returns to step 2), otherwise, a minimum spatial difference operator length 2M+1 which satisfies the allowable maximum approximation error xi and a difference coefficient corresponding to the minimum spatial difference operator length 2M+1 are determined, a next step is continued; and 4) seismic response numerical value simulation is performed on the target region, so that the simulation seismic records or seismic waves of the target region can be obtained.

The embodiments of the specification provide a finite difference method and device for a time-space high-order VTI rectangular grid. The method comprises: transforming a VTI elastic wave equation intoa matrix wave equation; expanding the matrix wave equation to a time fourth-order accuracy to obtain a discrete wave equation; calculating a spatial partial derivative based on the discrete wave equation; and calculating an optimized finite difference coefficient based on the spatial partial derivative. The method can effectively improve the time dispersion accuracy and improve the computationalefficiency of wavefield extrapolation.

The invention discloses a three-dimensional elastic wave field numerical simulation method and system based on staggered grid low-rank finite difference. The method comprises the following steps: constructing a staggered grid elastic recursion time integral operator; performing low-rank decomposition on the staggered grid elastic recursion time integral operator to obtain an elastic recursion time integral operator based on low-rank decomposition; calculating a staggered grid finite difference coefficient based on low-rank decomposition on the basis of an elastic recursion time integral operator based on low-rank decomposition; and obtaining numerical discrete representation of a three-dimensional decoupled elastic wave equation based on the staggered grid finite difference coefficient of the low-rank decomposition, and performing numerical simulation by utilizing the elastic wave equation of the discrete representation to obtain a longitudinal and transverse wave vector wave field. According to the method, a frequency dispersion relation curve can be fitted at a high wave number position, so that the three-dimensional longitudinal and transverse wave vector wave field can be obtained through elastic wave field continuation, the precision in the time and space directions is high, and subsequent processing interpretation is facilitated.

The embodiment of the invention discloses a three-dimensional Lowrank finite difference wave field numerical simulation method and device and electronic equipment. The three-dimensional Lowrank finite difference wave field numerical simulation method comprises the following steps: acquiring a speed model and grid point information; constructing an elastic recursion time integral operator based on the obtained speed model and grid point information; obtaining a decomposed elastic recursion time integral operator based on the elastic recursion time integral operator; obtaining a finite difference coefficient based on the decomposed elastic recursion time integral operator; and performing wave field numerical simulation based on the finite difference coefficient and an elastic wave equation to obtain an elastic wave field. The purpose of improving the elastic wave field precision is achieved.