Active injection protection scheme for flexible HVDC grids based on amplitude of input impedance

High-voltage direct current(HVDC)grids require fast and reliable protection of the DC lines.The performance of traditional protection schemes is easily impaired by the limitations of the boundary condition and nonlinearity from the control of converters.One of the key technologies for flexible HVDC grids is the half-bridge modular multilevel converter(HB-MMC).Considering the high controllability of HB-MMC,this study proposes an active injection protection scheme to improve the reliability and sensitivity of the HVDC grid protection.The HB-MMC is used to inject a sinusoidal characteristic signal,at the specified frequency,into the DC lines.Then,the voltage and current at the specified frequency are extracted using the Prony algorithm to calculate the input impedance,which is used for the identification of internal and external faults.The active injection protection scheme was simulated for various cases in the simulation software Power Systems Computer Aided Design.The simulation results indicate that the proposed protection scheme is highly reliable and can overcome transition resistance.

RESEARCH ON INPUT IMPEDANCE OF DIPOLE ANTENNA IN GTEM CELL

The formula of input impedance of dipole antenna in Gigahertz Transverse ElectroM agnetic(GTEM) cell based on the dyadic Green's function is first obtained in this paper. The validation of the formula is verified by the results of theoretical derivation and simulation with well agreements. In comparison with the formula of input impedance in free space, the relationship between the change of input impedance with the length of antenna and the position of antenna in GTEM cell is obtained. In addition, some meaningful conclusions are presented, which not only can be referred by the further research of ElectroM agnetic Interference(EMI) measurements in GTEM cell, but also provide the theoretical basis for testing compensation and error analysis.

T-Y TUBE MODEL OF HUMAN ASCENDINGAORTIC INPUT IMPEDANCE

This paper proposed a T- Y tube model to simulate foe input impedance of arterial system. It improves and extends the asymmetric T-tube model which was firstproposed by O' Rourke[1] and developed laier by Liu et al.[2]. Based on foe asymmetricT-tube model. a T-Y tube model was proposed by adding branching tubes whichrepresem the iliac arteries.All the tubes are considered to be uniform,viscoelasticlongitudinally tethered cylindrical tubes.The upper tube terminates with a windkesselmodel, while the terminal arterioles of the lowr tube are expressed as a resistance.After proper eraluation of the parameters.the impedance of the arterial system iscalculated under normal physiological and hypertensive condition.The model canpredict impedance in good agreement with the experimentally obtained data no matterin normal physiological condition or in pathological condition In comparison with theasymmeric T-tube model,T- Y tube model is closer to anatomy structure of the human arlerial system and at the sametime much simpler than the extremely complex multiplebranching tube model Therefore it will be a valuable model in studying the influencesof various parameters on aorta impedance and ventricular-vascular coupling.

Input Impedance of a Tunable Rectangular Microstrip Antenna

Input Impedance of a Tunable Rectangular Microstrip Antenna...

Reflection Loss is a Parameter for Film,not Material

In studies of microwave absorption in the current literature,theories such as reflection loss,impedance matching,the delta function,and the quarter-wavelength model have been inappropriately applied.As shown in this case study,these problems need to be corrected as they are representative of similar work in the literature.

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.

Reference Design of ICRF Antenna for EAST

An antenna array suitable for plasma heating and current drive has been designed for the ion cyclotron resonance frequency range （ICRF） heating on the EAST superconducting tokamak. The ICRF heating is planned to operate in a frequency range of 30 MHz to 80 MHz and hence the antenna geometry is optimized for 55 MHz. The design is based on the conventional strap antenna element. The coupling properties of the antenna are calculated with a slab model of the plasma for the antenna simulation. The coupling code is extended for the analysis of the toroidal antenna array separated by septa.

Ultrasonic power features of wire bonding and thermosonic flip chip bonding in microelectronics packaging

The driving voltage and current signals of piezoceramic transducer (PZT) were measured directly by designing circuits from ultrasonic generator and using a data acquisition software system. The input impedance and power of PZT were investigated by using root mean square (RMS) calculation. The vibration driven by high frequency was tested by laser Doppler vibrometer (PSV-400-M2). And the thermosonic bonding features were observed by scanning electron microscope (JSM-6360LV). The results show that the input power of bonding is lower than that of no load. The input impedance of bonding is greater than that of no load. Nonlinear phase, plastic flow and expansion period, and strengthening bonding process are shown in the impedance and power curves. The ultrasonic power is in direct proportion to the vibration displacement driven by the power, and greater displacements driven by high power (>5 W) result in welding failure phenomena, such as crack, break, and peeling off in wedge bonding. For thermosonic flip chip bonding, the high power decreases position precision of bonding or results in slippage and rotation phenomena of bumps. To improve reliability and precision of thermosonic bonding, the low ultrasonic power (about 1-5 W) should be chosen.

Corner Fed Microstrip Antenna Analysisfor Dual Polarization

This paper investigates a corner fed microstrip patch antenna by means of the cavity model with proposed feed modeling. The input impedance and radiation patterns for a corner feed are calculated. The mutual coupling between two corner feeds is investigated. An improvement in mutual coupling has been found for corner feeds relative to edge feeds, which is helpful for the design of dual polarized antenna arrays in wireless communication and radar applications.

NEW METHOD OF CALCULATING SHORT CIRCUIT LONG DISTANCE EHV AC TRANSMISSION LINES

In this paper a practical but sufficiently accurate method of calculating transient components in short circuit currents and voltages is proposed. It enables to find the roots of the characteristic equation of high order without forming and solving it. This method is convenient to use especially in case of complicated expansionary power systems.

Electromagnetic Modeling of a Planar Structure Integrating a Via-Hole Using the Method FWCIP

We present in this paper a new formulation of the iterative method FWCIP “Fast Wave Concept Iterative Process” based on the wave concept. It calculates the electromagnetic parameters of a planar structure including a via-hole. This is modelled by the electromagnetic field that it creates in the structure. The validation of results found by this new formulation is ensured by comparison with those obtained by HFSS “high frequency structural simulator” software from Ansoft. They show that they are in good agreement.

Design and optimization of CMOS LNA with ESD protection for 2.4 GHz WSN application

A new optimization method of a source inductive degenerated low noise amplifier（LNA） with electrostatic discharge protection is proposed.It can achieve power-constrained simultaneous noise and input matching. An analysis of the input impedance and the noise parameters is also given.Based on the developed method,a 2.4 GHz LNA for wireless sensor network application is designed and optimized using 0.18-μm RF CMOS technology. The measured results show that the LNA achieves a noise figure of 1.59 dB,a power gain of 14.12 dB, an input 1 dB compression point of-8 dBm and an input third-order intercept point of 1 dBm.The DC current is 4 mA under a supply of 1.8 V.