Abstract ：

This paper designs a three-axis closed-loop fluxgate system for geophysical prospecting, which contains excitation, induction, and feedback circuits. By analyzing and comparing the noise levels before and after the system operation, it is concluded that the main factor affecting the fluxgate performance is the excitation circuit noise. By analyzing the principle of fluxgate, the noise on the induction signal and feedback signal can reduce the accuracy of fluxgate and even lead to system instability in serious cases. In this paper, a passive filter circuit is designed to reduce the noise associated with the fundamental frequency from the source to ensure stable operation and improved performance of the system. Simulation and experimental data show that after using the filter circuit, the secondary frequency noise level of the induction signal and the feedback signal noise level are reduced by 10 times, and the trend capturing capability under external magnetic field is greatly improved.

Keyword ：

second harmonics second harmonics filter filter noise noise Fluxgate Fluxgate

Cite：

Copy from the list or Export to your reference management。

Abstract ：

SiC MOSFETs have an excellent characteristic of high switching speed, which can improve the efficiency and power density of converters significantly. However, the fast switching processes of SiC MOSFETs cause serious crosstalk problems in bridge-arm configurations, which restricts the devices' performances. This paper presents a detailed and accurate improved crosstalk analytical model, which takes into account the nonlinear capacitances, the parasitic inductances, the reverse recovery characteristics of the anti-parallel diodes, and the nonlinear voltage switching and damping oscillation process. The novelty of the proposed model lies in the fact that under the condition of comprehensively considering all these non-ideal factors of the bridge-arm, the effects of multi-parasitic elements and multi-variables coupling to the crosstalk are hierarchically divided. The parasitic elements and their correlations are described in detail and the direct and indirect variables' impacts are clearly traced. Thus, according to the different variables switching stages, the influence processes of these parasitic elements and variables can be integrated and a complete equivalent analytical model of the crosstalk process can be derived. The simulation and experiment platforms are established and a series of experimental verifications and comparisons prove that the model can replicate experimental measurements of crosstalk with good accuracy and detail.

Keyword ：

analytical model analytical model SiC MOSFETs SiC MOSFETs crosstalk crosstalk bridge-arm bridge-arm

Cite：

Copy from the list or Export to your reference management。

Abstract ：

Dielectric metamaterials have been proved to have broad applications in the microwave and optical frequency bands. However, as the components of the communication system shrink, the coupling effects caused by tight arrangements between the dielectric structures have not been carefully studied enough yet. In this paper, the deep coupling effects in limited space between the adjacent dielectric metamaterials cubes are investigated. According to the correlation between the coupling effect and the incident wave, the influence of coupling effect on the scattering characteristics of the structure is studied from three aspects: coupling effect parallel to the wave vector/electric field/magnetic field, respectively. Field distributions and constitutive parameters are also demonstrated to illustrate the relationship between the coupling effects and scattering coefficients.

Keyword ：

Mie resonance Mie resonance Dielectric metamaterials Dielectric metamaterials Coupling effects Coupling effects

Cite：

Copy from the list or Export to your reference management。

Abstract ：

Polarization has always been an important issue in modern communication systems, especially in sensitive measurements. Conventional polarization converters show limited applications due to their large size and narrow bandwidth. In this paper, we demonstrate an ultra-wide band, multifunctional, and highly efficient metamaterial-based polarization converter that is capable of converting a linearly polarized wave into its cross-polarized wave and circularly polarized wave over different frequency bands. The design principle is based on the field transformation theory and the anisotropic plate is made with high/low permittivity strip metamaterials. The simulation results show that the metamaterial-based polarization converter is able to achieve linear-to-linear conversion over 11.5-12.6 GHz, and linear-to-circular conversion over two frequency bands, 3.0-11.5 GHz and 12.6-17.0 GHz, with an average polarization conversion efficiency over 90%. The polarization converter proposed in this paper provides an important stepping stone for future communication systems' polarization control and can also be extended to higher frequency bands.

Keyword ：

polarization conversion polarization conversion ultra-wide band ultra-wide band high efficiency high efficiency metamaterial metamaterial

Cite：

Copy from the list or Export to your reference management。

Abstract ：

A novel active soft-switching converter is presented for an multi-transient electromagnetic method (MTEM) transmitter. The topology and operation principle of the MTEM transmitter are introduced in detail. Compared with the conventional converter, the proposed converter can operate in passive, single active and dual active soft-switching modes to achieve zero voltage switch over the entire load range, and the output power is greatly expanded. MTEM transmitter has the characteristics of large output-power, high-efficiency and strong-stability. The research has provided a solution for the development of other transmitters. At present, a 50 kW prototype has been completed and achieves 1 000 V/50 A output in the field. © 2019, Shanghai Jiao Tong University Press. All right reserved.

Keyword ：

Power converters Power converters Zero voltage switching Zero voltage switching Transmitters Transmitters Transient analysis Transient analysis

Cite：

Copy from the list or Export to your reference management。

Abstract ：

In order to improve the power factor and power density of electromagnetic transmitter, and make the transmitter small in size and light in weight, a novel electromagnetic transmitter circuit based on pulse width modulation (PWM) rectifier is presented in this paper. Parameters for the permanent synchronous generator (PMSG) PWM rectifier in the transmitter are designed. First, the mathematical model of the PMSG PWM rectifier is established, and then based on the flux oriented control theory in motor speed control system, a double closed loop control strategy, which consists of a decoupling current controller and an outer voltage controller is proposed. The active and reactive current decoupling control is obtained. To improve the dynamic performance and stability of the PMSG PWM rectifier, parameters in the PI controller are designed. Simulation and experimental results show that the proposed transmitter can not only meet the needs of geophysical exploration, but also has the advantages of simple structure, high power factor and low current harmonics. The proposed design method of controller can effectively determine the PI parameters and simplify control system. © 2018, Shanghai Jiao Tong University Press. All right reserved.

Keyword ：

Electric power factor Electric power factor Rectifying circuits Rectifying circuits Closed loop control systems Closed loop control systems Transmitters Transmitters Electric machine theory Electric machine theory Synchronous generators Synchronous generators Voltage control Voltage control Electric machine control Electric machine control Electric rectifiers Electric rectifiers Permanent magnets Permanent magnets Control systems Control systems Controllers Controllers Pulse width modulation Pulse width modulation

Cite：

Copy from the list or Export to your reference management。

Abstract ：

Compared with carrier based sinusoidal pulse width modulation (SPWM), space vector pulse width modulation (SVPWM) is widely used because of its higher current (voltage) utilization factor. In current source converter (CSC), SVPWM technique is harder to achieve than voltage source converter (VSC). To make the implementation of CSC SVPWM technique easier, this paper presents an indirect PWM method, which states that the modulation strategy of three phase CSC can be got from those used in three phase VSC by transforming bi-logic signals to tri-logic signals. In contrast to existing methods, a seven-segment modulation method is proposed. The presented method is validated by simulations, which show that the indirect PWM method has many advantages of easy implementation, low harmonic of AC side current, and low ripples of DC side current, etc.

Keyword ：

SVPWM SVPWM CSC CSC tri-logic tri-logic indirect PWM indirect PWM seven-segment modulation seven-segment modulation

Cite：

Copy from the list or Export to your reference management。

Abstract ：

The marine controlled source electromagnetic transmitting method could greatly improve the success rate of the offshore drilling and reduce drilling risk greatly. So it has been widely used in the abroad exploration industry of marine oil and gas in recent years. As a primary means of subsea communications, power line communication (PLC) system plays a major role in the marine electromagnetic exploration system. The communications platform of marine controlled source electromagnetic transmission system has been built by PLC system and the LabVIEW software in this paper. The GPS module has been used for time synchronization in this platform. The communication between the deck control platform and subsea uses the PLC system. And marine transmitter control platform could timely display and save the information of the operating, operating current and operating frequency in the subsea system. The experiment results verify that this platform could work stably for a long time and have the high transmission rate about 1kb / s.

Keyword ：

marine electromagnetic transmitting system marine electromagnetic transmitting system the deck control platform the deck control platform LabVIEW LabVIEW PLC system PLC system

Cite：

Copy from the list or Export to your reference management。

Abstract ：

The Forward Switch mode power supply is good selection for power supplies of Unmanned Aerial Vehicle (UAV). Compared with the conventional forward converter, there is one auxiliary switch in the active clamp forward converter to recycle the energy stored in the transformer leakage in order to minimize the voltage stress of the main switch. The power system is designed and the operation characteristics of the active switching power supply are revealed by analysis a typical second-order system in this paper. Active Clamp Forward Converter reduce the generation of EMI, the EMC of UAV equipment is greatly improved. The results of the analysis are verified by SPICE simulation.

Keyword ：

second-order system second-order system Active Clamp Active Clamp EMI EMI Forward Converter Forward Converter

Cite：

Copy from the list or Export to your reference management。

Abstract ：

Based on the principle of the three phase voltage source PWM rectifier, firstly, describes the topology of the three-phase VSR, and establishes the three-phase VSR's mathematical model based on the three-phase stationary symmetric coordinate system (a,b,c) and two-phase synchronous rotating coordinate system (d,q); then analysis the three-phase VSR's control strategy, and discusses the feedforward decoupling control strategy of the inner current loop, the outter voltage loop control strategy and the Space Vector PWM (SVPWM) control strategy. Secondly, builds a simulation model, simulates it in Matlab\Simulink environment.The simulation results show that the system has good current waveform of AC side current, high system stability, fast dynamic response speed, and can realize two-way flow of energy, energy feedback, and unit power factor control. © (2013) Trans Tech Publications, Switzerland.

Keyword ：

MATLAB MATLAB Mathematical models Mathematical models Innovation Innovation Pulse width modulation Pulse width modulation Dynamic response Dynamic response Computer simulation Computer simulation System stability System stability Manufacture Manufacture Electric power factor Electric power factor

Cite：

Copy from the list or Export to your reference management。