Effects of O_(2) addition on the plasma uniformity and reactivity of Ar DBD excited by ns pulsed and AC power supplies

Dielectric barrier discharges(DBDs)have been widely used in ozone synthesis,materials surface treatment,and plasma medicine for their advantages of uniform discharge and high plasmachemical reactivity.To improve the reactivity of DBDs,in this work,the O_(2) is added into Ar nanosecond(ns)pulsed and AC DBDs.The uniformity and discharge characteristics of Ar ns pulsed and AC DBDs with different O_(2) contents are investigated with optical and electrical diagnosis methods.The DBD uniformity is quantitatively analyzed by gray value standard deviation method.The electrical parameters are extracted from voltage and current waveforms separation to characterize the discharge processes and calculate electron density n_(e).The optical emission spectroscopy is measured to show the plasma reactivity and calculate the trend of electron temperature T_(e) with the ratio of two emission lines.It is found that the ns pulsed DBD has a much better uniformity than AC DBD for the fast rising and falling time.With the addition of O_(2),the uniformity of ns pulsed DBD gets worse for the space electric field distortion by O_(2)^(-),which promotes the filamentary formation.While,in AC DBD,the added O_(2) can reduce the intensity of filaments,which enhances the discharge uniformity.The ns pulsed DBD has a much higher instantaneous power and energy efficiency than AC DBD.The ratio of Ar emission intensities indicates that the T_(e) drops quickly with the addition of O_(2) both ns pulsed and AC DBDs and the ns pulsed DBD has an obvious higher T_(e) and n_(e) than AC DBD.The results are helpful for the realization of the reactive and uniform low temperature plasma sources.

Overview of Circuit Topologies for Inductive Pulsed Power Supplies

The pulsed power supply(PPS)is one important component in the electromagnetic launch system.The inductive PPSs have attracted researchers’attentions with the major advantages of high energy storage density(over the capacitive PPSs)as well as simple structure and easy control(over the rotating mechanical PPSs).As for the inductive PPSs,the circuit topology of the basic module will directly determine the comprehensive performance of the whole system.From the perspectives of working principles,strengths,weaknesses,and comprehensive performance,this paper presents a historical and technical review of the major circuit topologies for the inductive PPSs.

Inverter power supply system for high-power twin-wire pulsed GMAW

A type of novel inverter power supply system for high-power twin-wire pulsed gas metal arc welding （GMAW） is presented mainly for dealing with the disadvantages of the conventional power supply for twin-wire pulsed GMA W of which the output power is generally difficult to increase due to limitations of the power of semiconductors and the power density of magnetic devices. In the power supplies for the master and slave arcs, the digital signal processor （DSP） TMS320F28335 is used to form the DSP- based synergic control system for parallel high-power pulsed GMA W, which achieves high-power output of two parallel inverters controlled by a single DSP ; master-slave communication is achieved by using e controller area network （eCAN）module of DSP, thas realizing anti-phase pulse output of high-power twin-wire pulsed GMA W and reducing the interference between twin arcs. The experiment results demonstrate that the designed inverter power supply system for high-power twin-wire pulsed GMAW can bring about high-power efficiency of welding, stable welding process and proper formation of welds.

CLOSE-LOOP DESIGN OF PULSE POWER SUPPLY FOR ELECTRICAL DISCHARGE MACHINING

The dynamic performance and the stability are essential for a system. A new circuit topology used for electrical discharge machining (EDM) power and made up of complex-pulse (voltage-pulse and current-pulse) is presented. The large-signal model of it is also derived. Based on the comprehensive analysis of the system model, the compensator is designed to make the system match better and to improve its dynamic performance and the stability under perturbations. Finally, the design methods and the analysis are verified by simulation and experimental results.

Design and manufacture of a 100 kA coaxial pulsed power cable for plasma generator and PPS in ETC guns

Based on our previous pulsed current and internal overvoltage test data and the experience of common commercial high power cables,a 100 kA coaxial pulsed power cable is designed and manufactured to adapt the coaxial electric energy breech transmission between the plasma generator and the pulsed power supply(PPS) in electrothermal-chemical(ETC) guns.The index parameters are analyzed and determined.Semi-conductor layers and a shield stiffener are introduced to prevent the deformation and burst of the pulsed power cable structurally.The semi-conductor layer can eliminate the air gap and balance the electric field in the cable.The shield stiffener can multiply the mechanical strength to restrain the strong electrodynamic force produced by the core dislocation of the outer conductor.The multi-coupling of electromagnetic field,stress field and thermal field analysis are established to assist in aided design of electrical strength,mechanical strength and temperature rise characteristics.Both a DC voltage withstand test and pulsed discharge tests are introduced to verify and inspect the performance and dynamic response of the pulsed power cable.The 25 kV/5 min DC voltage withstand test result shows that the sample leakage current is nearly 3 μA and no abnormal phenomena of the pulsed power cable sample occurred.The pulsed discharge tests show that the sample can sustain the 100 kA peak current.Furthermore,this 100 kA coaxial pulsed power cable can satisfy the ETC test requirements.

Design and Simulation for the Pulse High-Voltage DC Power Supply (HVPS) of 1.2 MW/2.45 GHz HT-7U Lower Hybrid Current Drive System

The superconducting tokamak HT-7U [1] has been designed by the Institute of Plasma Physics since 1998 and will be set up before 2003. The 1.2 MW /2.45 GHz HT-7U LHCD (Lower hybrid current drive) system which being the most efficient non-induction device can heat the plasma and drive the plasma current has been efficiently in operation 'owl and a particular design of the 2.8 MW/-35 kV high-voltage DC power supply has been already completed and will apply to the klystron of LHCD on HT-7 and the future HT-7U, and the project of the power supply has been examined and approved professionally by an authorized group of high-level specialist in the institute of Plasma Physics. The detailed design of the power supply and the simulation results are referred in the paper.

Pulse Power Supply for Plasma Dynamic Accelerator

A new concept of a coaxial plasma dynamic accelerator with a self-energized magnetic compressor coil to simulate the effects of space debris impact is demonstrated. A brief description is presented about the pulse power supply system including the charging circuit, start switch and current transfer system along with some of the key techniques for this kind of accelerator. Using this accelerator configuration, ceramic beads of 100 μm in diameter were accelerated to a speed as high as 18 km/sec. The facility can be used in a laboratory setting to study impact phenomena on solar array materials, potential structural materials for use in space.

Long-pulse power-supply system for EAST neutral-beam injectors

The long-pulse power-supply system equipped for the 4 MW beam-power ion source is comprised of three units at ASIPP（Institute of Plasma Physics, Chinese Academy of Sciences）： one for the neutralbeam test stand and two for the EAST neutral-beam injectors（NBI-1 and NBI-2, respectively）. Each power supply system consists of two low voltage and high current DC power supplies for plasma generation of the ion source, and two high voltage and high current DC power supplies for the accelerator grid system. The operation range of the NB power supply is about 80 percent of the design value, which is the safe and stable operation range. At the neutral-beam test stand, a hydrogen ion beam with a beam pulse of 150 s, beam power of 1.5 MW and beam energy of 50 ke V was achieved during the long-pulse testing experiments. The result shows that the power-supply system meets the requirements of the EAST-NBIs fully and lays a basis for achieving plasma heating.

The Power Supply System for HL-2A Tokamak's Magnetic Field

The highpower pulsed power supply system for the magnetic field of the HL-2A Tokamak is described in this paper. The total output power of its eight magnetic field power supply units of nearly 250 MW. Their highest DC output voltage and current are 3510 V and 45 kA, respectively. All the units are operated in a pulsed mode. The pulse duration is 5 s, and the cyclic period is 15 min. The power supply system consists mainly of pulsed flywheel motor generators, rectifying transformers, thyristor converters, diode rectifiers and switches. The system incorporates many key technologies-supply equalization with two generators and four diode bridges, constant-angle phase triggers with a wide frequency range, current equalization, a status detector for the high current 6-phase converter, and advanced monitoring based on a programmable logic computer and engineering parameter measurement. The experimental results show that the performance of the power supply system satisfies the requirements of HL-2A experiments very well.

Optimization Design for a High Voltage DC Power Supply Module Based on PSM Technology

Pulse step modulator （PSM） topology is applied to the EAST auxiliary heating system, which consists of a neutral beam injection （NBI） and the related microwave heating system. This paper firstly analyzes the merits and demerits of the traditional PSM modules adopted by other international companies, and then optimizes the topology of the module using the analysis results. Finally, a new topology for the PSM module （a three-phase neutral-point diode-clamped rectifier） is proposed. This new module overcomes the problems of traditional modules and has better cost-effective performance. The experimental results verify that the new module is feasible for engineering applications.

Fusion power supply advances by the J-TEXT engineering team

To meet the stringent requirements of the fusion power supply for large-scale fusion devices,the J-TEXT engineering team has carried out key technology research and applications in several important directions of fusion power supply.This article presents the advances made by the J-TEXT engineering team in recent years in the following areas:(1) a high-voltage power supply for an auxiliary heating system;(2) a breakdown protection device for an auxiliary heating power supply;(3) magnetic field compatibility;(4) a high-voltage pulsed power supply for a fieldreversed configuration;(5) a large physics experimental facility control system.The research backgrounds,technical progress,test results,applications,summaries and prospects are described in detail in each part.These innovative research results and valuable engineering experience can promote the progress of fusion power supply technology,and also lay a foundation for the development of power supplies with higher parameters in the future.

A type of inverter power supply based on harmonic elimination PWM control

In order to output sine wave with small degree of distortion and improve stability,a type of inverter power supply is designed based on harmonic elimination pulse-width modulation(PWM)control.The rectifier and filter are added to input circuit of the inverter.Single-phrase full-bridge inverter performs the function of converting direct current into alternating current(DC/AC).In the control circuit,single chip micyoco(SCM)AT89C2051 is used for main control chip to accomplish the hardware design of the control system.A given value of output frequency of the inverter is input in the way of coding.According to the output frequency code which is read,SCM AT89C2051 defined harmonic elimination PWM control data which will be selected.Through internal timing control,the switches are switched under this provision of PWM control data.Then the driving signals of the switches in the inverter are output from I/O of SCM AT89C2051 to realize harmonic elimination PWM control.The results show that adding Newton homotopic algorithm of harmonic elimination PWM control to corresponding software of the control system can make the quality of output voltage of the inverter higher and it will have broad application prospects.

Design and Implementation of Smart Power Voltage and Frequency Synchroniser in Power Distribution System

Voltage and frequency are usually considered and assessed independently in the design and operation of electrical networks. However, these two are linked. Each and every malfunctioning electrical system has an impact on both voltage and frequency. This paper presents the opportunity for monitoring the distributed electrical energy by means of a system that monitors, controls, and provides a breakpoint based on high or low voltage and frequency tripping mechanism that avoids any damage to the load. The designed system comprised a switch mode power supply (SMPS), a direct digital synthesizer (DDS), and PIC16F876A microcontroller techniques for stable voltage and frequency outputs. Proteus design suite version 8.11 software and Benchcope SDS1102CN were used for modeling and simulation. The hardware prototype was implemented at a telecom cell site for data capturing and analysis. Test results showed that the implementation of the prototype provided stable and constant outputs of 222 V/50 Hz and 112 V/60 Hz which constituted 99% and 99.8% efficiency for voltage and frequency performance respectively. The paper also discusses different technologies that can be adopted by the system to mitigate voltage and frequency effects on customer appliances.

基于DDS的数字脉冲电火花沉积电源研究

在电火花沉积加工中,脉冲电源的放电参数对沉积效果和加工效率有重要影响。针对传统电火花沉积电源放电参数可控性差的问题,基于直接数字频率合成(DDS)技术全数字化调制、输出稳定的特性,设计了一种数字脉冲电火花沉积电源。以单片机和DDS芯片为核心来控制斩波电路输出加工脉冲,可实现放电电压、频率等参数的较精确控制以及宽范围内的无极调节。经测试,控制及驱动模块输出信号稳定、准确且频率误差在1 Hz以内,放电电压波形可控性好,满足电火花沉积加工的要求,可用于电火花沉积加工基础研究。

局部干法水下快频脉冲MIG焊电源研制

针对复杂水下环境焊接过程对焊接电源超高动特性与精确控制需求,设计基于SiC模块的快频脉冲焊接电源功率主电路,开发全数字化控制系统,研制出局部干法水下快频脉冲MIG焊电源(local dry underwater fastfrequency pulsed MIG,LDU-FFPMIG).研制的LDU-FFPMIG焊接电源额定输出电流为400 A,能精确输出多种0~30 kHz的快频脉冲电流波形,快频脉冲电流幅值高达200 A.提出LDU-FFPMIG焊接新工艺,将快频脉冲应用到304不锈钢局部干法水下MIG焊接,探究快频脉冲对传统局部干法水下脉冲MIG焊的影响.结果表明,研制的LDU-FFPMIG焊接电源能够实现稳定的局部干法水下MIG焊,可获得良好的焊缝成形;快频脉冲电流的引入可显著提高电弧能量密度和焊接稳定性,减小熔宽(B)、增大熔深(H),焊缝成形系数(B/H)减小约30%,并且可以细化晶粒.

车载逆变电源的设计与实现

为解决车载电源的转化问题,提出一种将汽车车载电源从直流12 V转化为交流220 V的车载逆变电源设计方法。该方法将直流12 V作为输入,通过前级升压和后级逆变2个功率转换电路,得到220 V/50 Hz的正弦交流电压。前级升压电路以SG3525作为主控芯片,采用推挽变换电路拓扑结构,利用高频变压器进行隔离升压,通过设计直流母线电压负反馈电路,避免出现直流母线电压的过压;后级逆变电路以EG8010作为主控芯片,采用全桥拓扑结构和SPWM控制技术,通过设计过压过流保护电路和过温保护电路,避免电路过压和过温。实验结果表明,该车载逆变电源在输入直流电压为(12±1.5) V的范围内均可输出稳定的交流电压(219.5~220.1 V),且整机测试效率保持在97.5%左右,具备良好的参数性能。

基于COMSOL 的不同温度气体脉冲放电特性的数值模拟研究

为了研究基于脉冲电源的线管式静电除尘器的放电特性,使用COMSOL软件建立了空气放电模型。在实验参数下模拟了空气放电,模拟结果与实验数据结果吻合较好。探究峰值电压、电极尺寸及气体温度等因素对放电特性的影响。结果表明,随着峰值电压及温度的升高,放电空间电子及离子密度逐渐增大,且高密度区域范围逐渐增大。电极半径尺寸越小,放电效果越好,放电空间电子及离子密度越高。研究了不同温度下反应速率与热电子发射对气体放电的影响,发现温度较高时热电子发射对放电具有显著的增强效果,大大提高了放电区域的电子及离子密度。

基于GaN的开关线性复合高速随动脉冲负载直流变换器

有源相控阵雷达发射机收发组件工作在高频脉冲负载模式,这对其供电电源的负载动态性能提出了很高要求。该文针对高速负载切换的二次DC-DC电源,提出开关线性复合并联结构的脉冲负载变换器及其相应的控制策略。基于器件级环路建模的方法有效提升了线性稳压电路的环路带宽,使其进行快速功率跟踪,并设计基于GaN的低阻抗交错并联Buck变换器,使其以较快的速度高效地提供主要脉冲功率。针对重复频率50 kHz、峰值功率120 W的高频模拟雷达脉冲负载,该文搭建脉冲电流上升下降时间50 ns以内的脉冲电源原理样机,输出电压跌落小于5%。实验结果表明所提方法能够有效改善脉冲电源的动态性能。

超导储能电感用于重接型电磁推进电源的研究

为了验证高温超导储能电感作为重接型电磁推进脉冲电源的可行性,采用Ansoft Maxwell 3D建立了重接型电磁推进器瞬态仿真模型,脉冲电源的设计结合了多模块储能电感串联充电和并联放电的模式,电路中采用转换电容器限制断路开关工作过程中的高电压。电感和电容参数都对最佳触发放电位置有一定的影响,即对驱动线圈电流脉冲的上升沿时间有影响。因为驱动线圈建立磁场的速度决定抛体感应出的涡流大小,抛体受到的驱动力与驱动线圈磁场大小和磁场建立的速度都有关。在多级推进系统的参数设计时,除了减小触发放电位置外,还需适当地减小驱动线圈的电感和减小转换电容的参数。

大功率高能脉冲激光电源设计

根据YAG激光器对大功率高能量脉冲电源的应用需求,设计了一种大功率脉冲激光电源,可实现高脉冲能量重复频率输出及充电电压灵活调控。前级充电网络采用串联LC谐振变换器,后级脉冲形成网络选择晶闸管触发LC放电电路。最终,研制了1台7 kW实验样机,最大重复频率10 Hz,最高充电电压2.2 kV,可实现单脉冲最高700 J电能输出,满足大功率高能脉冲输出的应用需求,实验测试结果验证了设计的可行性。