Research on Magnetically Coupled Resonant Detection Method for Breakpoint of Four Mesh Grounding Grid

Magnetically coupled resonant technology is a novel method for solving the breakpoint locating of power grounding grid.But the method can only detect breakpoints of a single mesh grounding grid at present.In this paper,a magnetically coupled resonant detection method for four-hole grounding grid breakpoint is proposed.Firstly,the equivalent circuit model of the four mesh grounding grid with two types of breakpoints,namely edge branch and intermediate branch,is established.The input impedance and phase angle of the system are obtained by analyzing the equivalent capacitance and equivalent resistance in the model.Secondly,the magnetically coupled resonant physical process of grounding grid faults is solved via HFSS software.The magnetic field intensity and phase frequency characteristic curves of four mesh holes with different branches and positions of breakpoints and different corrosion degrees are studied,and an experimental system is built to verify the feasibility.The results show that under the condition of grounding grid buried depth of 0.5 m and input frequency of 1~15MHz,and there is an inverse relationship between equivalent capacitance and distortion frequency,the phase angle is positively correlated with the degree of corrosion of grounding grid,and the error of signal distortion frequency can be positioned at 5%.This paper provides some ideas for the application of magnetic coupling grounding grid detection technology.

Online frequency and power regulation scheme of magnetic coupled resonant wireless power transfer

In order to address the issues that the magnetic coupled resonant wireless power transfer （MCR-WPT） system is sensitive to the resonant frequency and that transmission power is difficult to control with the non-resistive load in the MCR-WPT, a single-side regulation scheme for frequency and transmission power online is proposed, which is based on the inherent constraint relationships the among system parameters in the primary side. Thus, the communication between the primary side and the secondary side is avoided. First, the transfer models of resistance-capacitance load and resistance- inductance load are established, respectively. Next, the relationship between the input voltage phasor and the input current phasor is used to recognize the load property and value. Then, the coaxial rotation of the stepper motor and the rotating vacuum variable capacitor is conducted to unify resonant frequency both in the primary side and the secondary side. Finally, the regulations of both frequency and amplitude of input voltage are made to guarantee transmission power under a new resonant frequency point the same as the one when the only pure resistance part of load is accessed under the former resonant frequency point. Both simulation and experimental results indicate that the proposed regulation scheme can track remnant frequency and maintain transmission power constant.

Large tunable FMR frequency shift by magnetoelectric coupling in oblique-sputtered Fe52.5Co22.5B25.0/PZN-PT multiferroic heterostructure

In this study, we observe a strong inverse magnetoelectric coupling in Fe52.5Co22.5B25.0/PZN-PT multiferroic heterostructure, which produces large electric field（E-field） tunability of microwave magnetic properties. With the increase of the E-field from 0 to 8 kV/cm, the magnetic anisotropy field Heffis dramatically enhanced from 169 to 600 Oe, which further leads to a significant enhancement of ferromagnetic resonance frequency from 4.57 to 8.73 GHz under zero bias magnetic field, and a simultaneous decrease of the damping constant α from 0.021 to 0.0186. These features demonstrate that this multiferroic composite is a promising candidate for fabricating E-field tunable microwave components.

Circuit model based design and analysis for a four-structure-switchable wireless power transfer system

The four-coil wireless power transfer(WPT)technology can effectively improve the transfer efficiency.The high efficiency,however,cannot be obtained along the whole transfer distance due to the phenomenon of frequency splitting in the over coupled region.Aiming at this limitation,this paper presents a switchable WPT system to improve the overall efficiency by changing the number of working coils.The switching conditions for the designed system are determined based on the analysis of the transfer efficiencies of four structures,which is deduced through modeling the equivalent circuits.The simulation results well comply with the experimental results and both of them indicate that the switchable system can greatly improve the overall transfer efficiency along the whole transfer distance.The overall efficiency of the experimental system can reach above 70%at9.97 MHz without additional complexity,which is higher than any single structure system.