A study of pulsed high voltage driven hollow-cathode electron beam sources through synchronous optical trigger

In this study,a pulsed,high voltage driven hollow-cathode electron beam sources through an optical trigger is designed with characteristics of simple structure,low cost,and easy triggering.To validate the new design,the characteristics of hollow-cathode discharge and electron beam characterization under pulsed high voltage drive are studied experimentally and discussed by discharge characteristics and analyses of waveform details,respectively.The validation experiments indicate that the pulsed high voltage supply significantly improves the frequency and stability of the discharge,which provides a new solution for the realization of a high-frequency,high-energy electron beam source.The peak current amplitude in the high-energy electron beam increases from 6.2 A to 79.6 A,which indicates the pulsed power mode significantly improves the electron beam performance.Besides,increasing the capacitance significantly affects the highcurrent,lower-energy electron beam more than the high-energy electron beam.

A Novel High Output Resistance Current Source Based on Negative Resistance

This paper presents a novel scheme for enhancing resistance that utilizes an equivalent negative resistance. Adopting this novel scheme in the proposed current source could remarkably boost its output resistance without requiring increased power supply. Simulation with 0.6μm CMOS process models shows that the output resistance of the novel current source can reach the order of 10^9Ω with a 1.04GHz bandwidth and only 10.6ppm/℃ in the range of -40～145℃.

Design and Realization of a High-Precision Numerical Control Current Source

The design adopts self-designed high accurate voltage source, Micro Control Unit (MCU), D/A converter and amplifier to control the on-state of Power MOS FET, to attain constant current. The closed loop system realizes constant current output of high-precision, presettable and step-by-step adjustable, and its output current data can be directly displayed by digital devices. Finally achieve a high-precision constant current source by locking output with closed hardware loop, closed software loop, software realtime integrating, real-time filtering. The role of software is to compensate the temperature variance of sampling resistances by data segment interpolation, while the linear interpolation compensation is applied to intersegments, which improves the output precision further. It has advantages on high precision, simple construction, performance stable, easy operation, low cost and loaded capability.

The Development of a Megawatt-Level High Current Ion Source

Neutral beam injection is one of the main plasma heating methods in nuclear fusion devices. In order to support the scientific study of the Experimental Advanced Superconducting Tokamak （EAST）, a megawatt-level high current ion source is designed and manufactured in the ASIPP, and the progress and preliminary test results will be presented in this paper.

Carrier phase shifted SPWM based on current sourced multi-modular converter for active power filter

A novel current-source active power filter (APF) based on multi-modular converter with carrier phase-shifted SPWM (CPS-SPWM) technique is proposed. With this technique, the effect of equivalent high switching frequency con-verter is obtained with low switching frequency converter. It is very promising in current-source APF that adopt super-conducting magnetic energy storage component.

Kuroshio warm filament and the source of the warm water of the Tsushima Current

Characteristics and evolution of the Kuroshio frontal eddies and warm filaments are analyzed according to two series of satellite images (March 5 to 7, 1986 and April 14 to 16, 1988). The results show that the frontal eddies in the East China Sea are generated at the shelf break and move along the continental slope at a speed of 15 cm/s with the Kuroshio. The frontal eddies occur about every 10 d and evolve to be warm filaments a few hundred km in length and 30-40 km in width in the area west of the Yaku-shima. Meanwhile, the existence of the warm filament was also found in the area by analysing the hydrographic data in the area west of Kyushu during May 24-June 5, 1988.The Kuroshio warm filaments move westward opposite to the Kuroshio and then turn northward at the shelf break and become the main source of the warm water of the Tsushima Warm Current. A simple dynamic explanation for the process is presented in this paper.

The Arc Regulation Characteristics of the High-Current Ion Source for the EAST Neutral Beam Injector

The arc regulation method is applied to the high-current ion source for high-power hydrogen ion beam extraction for the first time. The characteristics of the arc and beam, including the probe ion saturation current, the arc power and the beam current, are studied with feedback control. The results show that the arc regulation method can be successfully applied to ion beam extraction. This lays a sound foundation for the testing of a new ion source and the operation of a conditioned ion source for neutral beam injector devices.

Online Learning Control for Harmonics Reduction Based on Current Controlled Voltage Source Power Inverters

Nonlinear loads in the power distribution system cause non-sinusoidal currents and voltages with harmonic components.Shunt active filters(SAF) with current controlled voltage source inverters(CCVSI) are usually used to obtain balanced and sinusoidal source currents by injecting compensation currents.However,CCVSI with traditional controllers have a limited transient and steady state performance.In this paper,we propose an adaptive dynamic programming(ADP) controller with online learning capability to improve transient response and harmonics.The proposed controller works alongside existing proportional integral(PI) controllers to efficiently track the reference currents in the d-q domain.It can generate adaptive control actions to compensate the PI controller.The proposed system was simulated under different nonlinear(three-phase full wave rectifier) load conditions.The performance of the proposed approach was compared with the traditional approach.We have also included the simulation results without connecting the traditional PI control based power inverter for reference comparison.The online learning based ADP controller not only reduced average total harmonic distortion by 18.41%,but also outperformed traditional PI controllers during transients.

Theoretical analysis method for Howland current source design

The Howland current source （HCS） circuit is commonly used, e.g. in electrical impedance tomography （EIT） sys tems. It is important to optimise the design parameters, such as the output impedance, bandwidth, current stability and load range. While many people have used this circuit, it has not been systematically analysed. In this paper, a numerical method is proposed to analyse the characteristics of HCS. Based on a nonideal opamp model, general formulas and simplified for mulas for calculating the output impedance and the closeloop gain of HCS are deduced. From these formulas, the practical formulas are chosen and their effectiveness has been proven by analysis and experiment. The output impendence of two HCS circuits based on t^A741 and LM6365 are compared. The magnitudefrequency response and the relationship between the cur rent and the load of HCS are discussed.

Recent Developments of Modulation and Control for High-Power Current-Source-Converters Fed Electric Machine Systems

The pulse-width-modulated(PWM)current-source converters(CSCs)fed electric machine systems can be considered as a type of high reliability energy conversion systems,since they work with the long-life DC-link inductor and offer high fault-tolerant capability for short-circuit faults.Besides,they provide motor friendly waveforms and four-quadrant operation ability.Therefore,they are suitable for high-power applications of fans,pumps,compressors and wind power generation.The purpose of this paper is to comprehensively review recent developments of key technologies on modulation and control of high-power(HP)PWM-CSC fed electric machines systems,including reduction of low-order current harmonics,suppression of inductor–capacitor(LC)resonance,mitigation of common-mode voltage(CMV)and control of modular PWM-CSC fed systems.In particular,recent work on the overlapping effects during commutation,LC resonance suppression under fault-tolerant operation and collaboration of modular PMW-CSCs are described.Both theoretical analysis and some results in simulations and experiments are presented.Finally,a brief discussion regarding the future trend of the HP CSC fed electric machines systems is presented.

Magnetite Quartzite-Type Iron Ores – China's Most Important Current Iron Ore Source

China is abundant in iron-ore resources, with proven ore reserves of 576.62×10^8 t and proven reserves of 210×10^8 t, containing an average iron content of 33%. However, the rich iron-ore reserves of 10.85×10^8 t only account for 1.9% of all proven reserves. China＇s iron-ore resources are characterized by many lean ores and a few rich ones.

High Accurate Howland Current Source: Output Constraints Analysis

Howland circuits have been widely used as powerful source for exciting tissue over a wide frequency range. When a Howland source is designed, the components are chosen so that the designed source has the desired characteristics. However, the operational amplifier limitations and resistor tolerances cause undesired behaviors. This work proposes to take into account the influence of the random distribution of the resistors in the modified Howland circuit over the frequency range of 10 Hz to 10 MHz. Both output current and impedance of the circuit are deduced either considering or the operational amplifiers parameters. The probability density function due to small changes in the resistors of the circuit was calculated by using the analytical modeling. Results showed that both output current and impedance are very sensitive to the resistors variations. In order to get higher output impedances, high operational amplifier gains are required. The operational amplifier open-loop gain increases as increasing the sensitivity of the output impedance. The analysis done in this work can be used as a powerful co-adjuvant tool when projecting this type of circuit in Spice simulators. This might improve the implementations of practical current sources used in electrical bioimpedance.

Adaptive Continuous Current Source Drivers for 1-MHz Boost PFC Converters

针对高频功率因数校正（power factor correction，PFC）变换器，提出自适应电流源驱动电路（current source driver，CSD）。由于PFC变换器的占空比在一个输入工频周期内不断变化，半桥结构CSD驱动电路很难应用于PFC场合中。为了解决上述问题，提出全桥结构CSD电路。该CSD电路具有连续电感电流，且驱动电流会随着主功率MOSFET开关电流的自适应调整，以实现最优设计。详细给出工作原理、损耗分析和设计优化方法，并进行实验验证。

Improved power simulation of AlGaN/GaN HEMT at class-AB operation via an RF drain–source current correction method

A new modified Angelov current–voltage characteristic model equation is proposed to improve the drain–source current（Ids） simulation of an Al Ga N/Ga N-based（gallium nitride） high electron mobility transistor（Al Ga N/Ga N-based HEMT） at high power operation. Since an accurate radio frequency（RF） current simulation is critical for a correct power simulation of the device, in this paper we propose a method of Al Ga N/Ga N high electron mobility transistor（HEMT）nonlinear large-signal model extraction with a supplemental modeling of RF drain–source current as a function of RF input power. The improved results of simulated output power, gain, and power added efficiency（PAE） at class-AB quiescent bias of Vgs =-3.5 V, Vds= 30 V with a frequency of 9.6 GHz are presented.

Multilevel Current Source Converters for High Power Medium Voltage Applications

In medium voltage high power applications,multi-level current source converters(CSCs)are good candidate to increase system power region,reliability,and the quality of output waveforms.Compared with widely researched voltage source multi-level converters(MLCs),the current source MLCs have the advantages of inherent short-circuit protection,high power capability and high quality of output current waveforms.The main features of MLCs include reduced harmonics,lower switching frequency and reduced current stress on each device which is a particularly important for high power application with low voltage and high current requirements.This paper conducts a general review of the current research about MLCs in higher power medium voltage application.The different types of parallel structure based MLCs and the modulation methodologies will be introduced and compared.Specifically,the circuit analysis of the common-mode(CM)loop for parallel structures will be conducted,the common-mode voltage(CMV)and circulating current suppression methods developed on the base of multilevel modulations will be addressed.

Study on Short Circuit Current Calculation of Power System with UHVDC and New Energy Source

With the development of power system, the level of short circuit current will increase accordingly. In general, the influence of the HVDC system and the new energy source is not considered in the calculation of the short circuit current. For the power grid that short circuit current level closes to the interrupting capacity of circuit breaker, it’s necessary to fully consider all kinds of influence factors, careful checking, so as to obtain more accurate calculation results of short circuit current. In 2018, two ±800 kV high-power Ultra High Voltage Direct Current (UHVDC) transmission projects will be connected with Shaanxi power grid, accompanied by a lot of concomitant fossil-fuel generating plants as power resource, and also a large number of new energy source, includes wind power generation and photovoltaic power generation. Around one of the UHVDC converter stations, short circuit current may exceed the withstand limit of some certain circuit breakers. In order to get more accurate short circuit current calculation results, three measures are used: 1) contrastive calculation and analysis by algorithm based on schemes and algorithm based on power flow;2) analysis the influence of UHVDC by electromagnetic transient and electromechanical transient hybrid simulation;3) considered a detailed model of Doubly Fed Induction Generator (DFIG) with low voltage ride through characteristics. The calculation results shows that: in the typical operation mode of Shaanxi power grid of 2018, the original calculation results by conventional calculation method are coincident with the results by considering the influence of algorithms, UHVDC and DFIG in large, in which: the results of the algorithm based on power flow are smaller than that of the algorithm based on schemes about 2 - 8 kA;the steady values of the short circuit current provided by UHVDC converterstation (includes rectifiers and smoothing capacitors) are about 0 - 3 kA;the steady values of the short circuit current provided by DFIG are about 0 - 5 kA. The calculation results can provide reference for the selection of the circuit breaker, and it can be verified by fault recording data in the future.

A Single Phase Current Source PFC Converter Based on UC3854

A novel high-power-factor Buck type converter with average current control based on UC 3854 is proposed. The input current is directly controlled by average current control scheme to deliver sinusoidal input current and to gain a high power factor. The practical results, which illustrate the proposed control philosophy, were obtained from a 120 W AC/DC Buck type converter. The power factor can reach 0.97.

Development of data acquisition and over-current protection systems for a suppressor-grid current with a neutral-beam ion source

Neutral beam injection is one of the effective auxiliary heating methods in magnetic-confinementfusion experiments. In order to acquire the suppressor-grid current signal and avoid the grid being damaged by overheating, a data acquisition and over-current protection system based on the PXI（PCI e Xtensions for Instrumentation） platform has been developed. The system consists of a current sensor, data acquisition module and over-current protection module. In the data acquisition module,the acquired data of one shot will be transferred in isolation and saved in a data-storage server in a txt file. It can also be recalled using NBWave for future analysis. The over-current protection module contains two modes： remote and local. This gives it the function of setting a threshold voltage remotely and locally, and the forbidden time of over-current protection also can be set by a host PC in remote mode. Experimental results demonstrate that the data acquisition and overcurrent protection system has the advantages of setting forbidden time and isolation transmission.