10 results about "Electromagnetic current" patented technology

This invention discloses a method for obtaining the wide-angle single-station RCS of a medium target based on a compressed sensing algorithm. The steps are as follows: setting a wide-angle uniform incident plane wave illuminating the medium target; defining RWG basis functions and calculating the excitation vector for each incident angle; performing sparsification and compression on the excitation vectors respectively; generating the PMCHWT equations for the target surface and solving to obtain the compressed induced electromagnetic current matrix; recovering the original induced electromagnetic current matrix from each column of the compressed induced electromagnetic current matrix using the OMP algorithm; and calculating the radar cross section of the medium target based on the induced electromagnetic current vectors. This invention can obtain the RCS result at any angle with fewer PMCHWT equation solutions and combined with the OMP recovery algorithm, reducing the solution time for the wide-angle RCS of the medium target while ensuring accuracy.

The invention particularly relates to a random response analysis method for a piezoelectric-electromagnetic hybrid energy collector under pulsating wind excitation, and the method comprises the steps: building a mechanical vibration equation containing a galloping aerodynamic item and a time-delay feedback control item, and enabling the mechanical vibration equation to be combined with a piezoelectric voltage state equation and an electromagnetic current state equation to form an initial electromechanical coupling equation set; therefore, the mechanical end dynamics and the energy conversion effect of the two branches are simultaneously represented in the same model. Introducing the dimensionless fluctuating wind speed into galloping aerodynamic force and performing equivalent modeling by using multiplicative noise so as to explicitly map the fluctuating wind speed into a state-related random excitation item; voltage and current variables are equivalent to algebraic terms of displacement and speed by adopting harmonic transformation, and an equivalent decoupling system is obtained, so that model variable transformation is realized, and the analytical solution efficiency is improved; and finally, a steady-state probability density function is obtained based on energy envelope random averaging, and a random response analysis result is calculated according to the steady-state probability density function, so that a reliable basis is provided for evaluation of control parameters and energy harvesting performance.

This invention provides an integrated and accurate simulation method for electromagnetic scattering of partially rotating targets, comprising: modeling and setting system parameters; dividing the target into relatively stationary sub-regions, rotating sub-regions, and linked sub-regions, and establishing a rotationally symmetric equivalent surface to completely enclose the rotating sub-domains; establishing a global coordinate system and a local coordinate system; using a consistent mesh in the global coordinate system as the outer mesh, and independently meshing the local coordinate system as the inner mesh, and defining the inner and outer basis functions accordingly; calculating the self-acting operator, equivalent operator, coefficient solving operator, and interaction operator of the equation to be solved; updating the coordinate system rotation operator between the global and local coordinate systems, establishing and solving the equation to be solved for the partially rotating conductor target at the current moment, and then calculating the far-field scattering field at the current moment from the scattering electromagnetic current coefficient vector; repeating the first two steps until the calculation of the far-field scattering field at different sampling time points throughout the entire rotation cycle is completed. This method has a fast modeling speed.

The invention discloses an electromagnetic near-field scattering characteristic modeling calculation method based on half-space target source reconstruction and electronic equipment. The method comprises the following steps: modeling the ground into an infinite PEC, and constructing a surrounding surface for a target scatterer on the ground and a ground area in contact with the target scatterer; calculating an incident field of the incident wave on the surrounding surface, and solving equivalent electromagnetic current distribution on the surrounding surface by taking the incident field as an excitation source; removing a target scatterer in the surrounding surface, and performing integration on the equivalent electromagnetic current distribution by using a half-space green function to obtain a part of scattered field at the observation position; and calculating a background field of the observation position when only the incident field is incident on the infinite ideal electric conductor ground, and adding the background field and a part of the scattered field to obtain a total electromagnetic field of the observation point. Half-space target source reconstruction is carried out based on the Huygens equivalence principle, the model complexity is greatly reduced, the operation efficiency is remarkably improved, the problem of ground truncation is solved, and meanwhile, the method is suitable for far-field and near-field scenes.

The present application relates to a kind of vortex electromagnetic wave target high-frequency scattering calculation method based on equivalent edge electromagnetic current correction, belong to electromagnetic calculation field.Method includes: constructing target triangulation model and extracting convex split edge;Bessel vortex wave is decomposed into plane subwave superposition;The main scattering field under the irradiation of subwave is calculated using physical optics PO;Based on physical diffraction theory, the diffraction field of subwave in convex split edge is calculated using PTDEEC model of equivalent edge electromagnetic current;The main scattering field and edge diffraction field are superposed to obtain the modified total field, and the radar cross section (RCS) is calculated.The present application effectively corrects the diffraction error of traditional PO method at the edge of target by equivalent edge electromagnetic current, significantly improves the scattering calculation precision of large-size edge target under complex vortex beam irradiation, and provides more reliable high-frequency algorithm for radar target recognition and stealth design.

The current transformer secondary open circuit protection device is composed of a shell, a bimetallic strip, a thermal element resistance wire, a first lead, a movable contact, a static contact, a conductive metal sheet and a second lead, and has the advantages that inert gas is filled in a closed glass tube, glow discharge is generated through ionization, the bimetallic strip is heated to deform through heat of the glow discharge, and the current transformer secondary open circuit protection device is safe and reliable. The movable contact on the bimetallic strip is in contact with the static contact on the conductive metal sheet, so that the lead wire I and the lead wire II are conducted, and the K1 terminal and the K2 terminal on the secondary side of the current transformer are short-circuited, the short circuit of the open-circuit winding of the electromagnetic current transformer is achieved, high voltage generated by secondary open circuit is eliminated, and the electromagnetic current transformer has the advantages of long service life and low cost. The size is small, the mechanism is simple, and the device can be repeatedly used after faults disappear.

The invention provides a method and a system for calculating electromagnetic scattering characteristics of a complex target and a medium. The method comprises the following steps: dividing regions according to material distribution and splitting open regions into open regions and interfaces; constructing an electromagnetic current joint integral equation based on electric field and magnetic field continuity conditions; the equation is directly adopted in an open area, and a variable coefficient is introduced into an interface to correct a Robin transmission condition; constructing a matrix equation by using a full / semi-RWG primary function and combining a Galerkin method through a triangular surface element discrete grid; and after a generalized minimum margin method is adopted for solving, a scattering field and a radar scattering sectional area are calculated. According to the method, variable coefficient DDM, non-conformal mesh generation and discontinuous Galerkin technologies are fused, the problem of discontinuity of multi-scale adaptation and matrix construction is solved, calculation precision and efficiency are both considered, and the method is suitable for rapid calculation of electromagnetic scattering of complex targets.

This invention discloses an inter-well time-frequency electromagnetic data acquisition system and method based on a downhole current source. A time-frequency electromagnetic transmitter emits low-frequency time-frequency electromagnetic signal current between two or more wells. An array-type multi-component time-frequency electromagnetic data acquisition sub is used in the receiving well to acquire the inter-well time-frequency electromagnetic signals. Since one end of the time-frequency electromagnetic transmitter is downhole in the transmitting well, and the other end is grounded at the wellhead of the receiving well or connected to the metal casing, the time-frequency electromagnetic current emitted by the transmitter passes through the rock formations or reservoirs between the two or more wells, reaching the wellhead or casing of the receiving well, and simultaneously stimulating a low-frequency excitation polarization effect within the reservoir. Because this invention acquires low-frequency inter-well time-frequency electromagnetic data, the resistivity, polarizability, and IPR distribution of the rock formations between the two or more wells can be calculated through constrained inversion, enabling accurate evaluation of the oil and gas resources in the underground reservoirs.

This application provides a harmonic elimination method and apparatus for modular multilevel converter high-voltage direct current (HVDC) transmission, comprising: constructing a current and voltage measurement matrix based on the topology and electrical parameters of an electromagnetic current transformer, its secondary system, an electromagnetic voltage transformer, and its secondary system in the HVDC transmission system; constructing an HVDC transmission impedance model including current and voltage measurement components based on the main circuit topology of the HVDC transmission system and the current and voltage measurement matrix; analyzing the HVDC transmission impedance model under preset operating conditions to obtain the impedance matrix of the current and voltage measurement components; and determining the resonant frequency of the HVDC transmission using the impedance matrix of the current and voltage measurement components to perform harmonic elimination. This application can analyze the mismatch effects caused by the measurement components of the current transformer (CT) and its secondary system, and the current transformer (PT) and its secondary system, respectively, determine the system resonant frequency, and eliminate the resonance effect.

The invention discloses a residual magnetism detection and demagnetization method and device for an iron core of an electromagnetic current transformer. The method comprises the following steps: collecting a current signal and a voltage signal; performing harmonic analysis on the current signal; carrying out integration processing on the voltage signal; performing phase decomposition on the even harmonic component according to a magnetic flux fundamental wave phase, and extracting a residual magnetism correlation component; determining a normalized residual magnetism index according to the residual magnetism correlation component and the odd harmonic component; the controllable current source is connected in parallel with a secondary loop of the electromagnetic current transformer; and taking the normalized residual magnetism index as a closed-loop feedback signal to adjust the polarity and amplitude of the controllable direct-current component, so that the normalized residual magnetism index approaches zero. On the premise that the electromagnetic current transformer does not exit from operation and metering and protection functions of the electromagnetic current transformer are not interrupted, whether residual magnetism exists in the iron core or not and the level of the residual magnetism can be detected on line, closed-loop active demagnetization is automatically implemented when it is detected that the residual magnetism exceeds a safety threshold value, and the iron core is restored to a symmetrical magnetization working state without residual magnetism.