Search

There are few of transient control models are adapted to asynchronous induction coil launcher (AICL) with air core coil. Thus, many papers about AICL were written with the goal of increasing muzzle velocity of projectile. This paper concentrate on how to control the projectile speed and thrust accurately by using improved current filament (CF) method and variable voltage variable frequency (VVVF) scheme. The improved CF method contains mathematical model of three-phase inverter based on switch function, including conventional two level converter and cascaded multilevel converter models. The whole launch process is programmed with MATLAB. Simulation results show that this scheme have a smoother thrust fluctuation on projectile than other driving models. The motor parameters are changing with the temperature and frequency in launching process. Hence, the constant voltage frequency ratio (V/f) in this paper is more simple and reliable than vector control. To verify the control model and simulation results, a nine stages coil launcher prototype is constructed. The measured force and muzzle velocity are basically consistent with simulation results. It is proved that the improved CF method and VVVF strategy is feasible, and it is characterized by its small calculating amount that make it a valuable tool for design of AICL. The simple and excellent control of the thrust during launch process avoids load peaks, which means that the payload is handled more carefully compared to the classical launchers. [ABSTRACT FROM PUBLISHER]

The planned China fusion engineering test reactor (CFETR) needs one or more negative-ion-based neutral beam injectors (N-NBIs) with a beam energy of 500 or even 1000 keV. In order to prepare for CFETR, a prototype of CFETR N-NBI is being designed. The prototype needs an acceleration grid power supply (AGPS) rated at 200 kV/25 A with a maximum pulselength reaches to 3600 s. The AGPS adopted a single-stage inverter-type high-voltage power supply (HVPS). The output voltage ripple is an important specification of the AGPS, which can affect the efficiency and stability of N-NBI system by influencing the beam divergence. However, the conventional methods cannot be used to limit the output voltage ripple of the inverter-type HVPS used as AGPS of CFETR N-NBI prototype. This paper simplified the AGPS to an insulated three-phase three-level (TPTL) dc–dc converter connected with a dual dc link. The working process of the TPTL dc–dc converter with duty-cycle modulation has been analyzed, and two main continuous conduction modes are described. The influence of key parameters such as duty cycle of inverter, leakage inductance of transformer, and output current on output voltage ripple is analyzed. Based on the analysis results, a so-called combined control strategy was proposed to keep the output voltage ripple at a level. The proposed strategy is suitable for the cases where the object output voltage is below 175 kV. Some simulations were carried out by using MATLAB/Simulink. The results showed that the analysis in this paper is reliable and the proposed control strategy has a good performance. [ABSTRACT FROM AUTHOR]

The external bypass, as an important component of the international thermonuclear experimental reactor (ITER) poloidal field converter unit (PFCU), will provide a freewheeling loop for the load current to protect the magnets and PF converter modules from being damaged by overcurrent and overvoltage under fault conditions. The triggering bypass protection test is used to verify that the designed bypass is triggered normally and endure the rated load current. In this paper, a suitable test scheme is designed for triggering bypass protection test of ITER PFCU based on the PF converter integrated test platform at the Institute of Plasma Physics, Chinese Academy of Sciences. This test scheme includes the triggering bypass method, calculating the trigger angle of the converter in inverter and a method of reducing the bypass current to zero in the absence of ITER mechanical switch. The feasibility of the test scheme is successfully verified by the simulation results and test results, both of which prove that the external bypass of ITER PFCU is triggered normally and withstands the load current for 100 ms. Due to the integrated inductance of the actual dc output circuit, the actual transfer time of bypass current in the test is more than the simulation results. [ABSTRACT FROM AUTHOR]

In JT-60SA, the control of resistive-wall-mode (RWM) instabilities will also be realized with a dedicated active control system based on 18 in-vessel sector coils. Each coil will be fed independently by a dedicated fast inverter. Due to the outstanding dynamic performance required, new insulated-gate bipolar transistor modules based on silicon carbide (SiC) have been adopted. Being capable to switch at 30 kHz, these components, together with a very fast control system, allow reaching the required high dynamic performance with the simple and compact H-bridge topology. The RWM-PS will be the first power supply system for fast control of plasma instabilities in fusion experiments adopting SiC semiconductors. This paper gives an overview of the final design of the RWM-PS, with particular emphasis on its special features and the solutions implemented to satisfy the critical requirements. The issues related with the high switching frequency and the peculiar nature of the load will be treated in detail. [ABSTRACT FROM AUTHOR]

This paper presents the design and experimental results of the 36-kW pulsed-power supply for the xenon flash lamp. The continuous conduction mode series-parallel resonant converter is modified. This means that not only the few hundred kilohertz of high switching frequency is introduced to replace the resonant inductor with the leakage inductor of transformer but also the high output current is accomplished by using three-phase delta-connected transformers. In addition, the snubber capacitor of the inverter switches and the power factor correction module is both omitted in the compact structure. Although these main components have changed, the efficiency and power factor of the rated dummy load reach 96% and 0.96%, respectively. Within 36-kW average power, the proposed pulsed-power supply can generate as versatile combination of output pulse. For example, it can generate 20-ms pulse with 1-Hz repetition rate or generate 1-ms pulse with 20-Hz repetition rate. The used insulated gate bipolar transistor is protected from the turn-OFF peak voltage by the snubber circuit, and the effect of the snubber circuit is shown at the actual load condition. [ABSTRACT FROM PUBLISHER]

With the wide use of laser in industry, agriculture, medical, and military, the requirement of its preceding excitation power supply is also getting higher and higher. In this paper, a high-voltage repetition-frequency charging power supply used for pulsed laser is described, which uses the principle of series resonant and power electronic conversion. A high-frequency high-voltage transformer and a high-voltage silicon rectifier are also used to obtain a dc voltage, whose output power can reach up to 20 kW. The control system of the power supply is based on the digital signal processor, so that the output voltage can be regulated between 0 and 30 kV, and the repetition frequency can be regulated between 1 and 100 Hz. Some other functions have been designed, such as the two control modes of remote control by PC and local control by keyboard. To extend the application of this power supply, an external trigger control interface is also provided for the synchronization control of the power supply and other equipment of the pulsed laser system. In the experiment, the power supply that described in this paper was used as the preceding excitation power supply of the pulsed laser. The results of the experiment show that the power supply can work effectively. [ABSTRACT FROM PUBLISHER]

This paper shows how to use modular Marx multilevel converter diode ( \textM^3 CD) modules to apply unipolar or bipolar high-voltage pulses for pulsed power applications. The \textM^3 CD cells allow the assembly of a multilevel converter without needing complex algorithms and parameter measurement to balance the capacitor voltages. This paper also explains how to supply all the modular cells in order to ensure galvanic isolation between control circuits and power circuits. The experimental results for a generator with seven levels, and unipolar and bipolar pulses into resistive, inductive, and capacitive loads are presented. [ABSTRACT FROM AUTHOR]

This paper presents the design and development of a −100 kV, 20 A, all solid-state long-pulse modulator for driving high average power klystron amplifier. Modular design approach has been adopted for achieving the −100-kV output. Six dc–dc converters along with high-voltage high-frequency transformers are used for high-voltage generation. Low-loss insulated gate bipolar transistor (IGBT) switches in full-bridge configuration have been used for high-frequency switching. The IGBT-based inverter modules are delayed in phase by 120° with respect to each other. The switching frequency is 20 kHz. Output pulses of 1.6-ms pulsewidth, 70- $\mu \text{s}$ rise time, and 65- $\mu \text{s}$ fall time have been achieved at the modulator output. A droop of ±1% is achieved using a simple feedforward correction control technique. The performance of the modulator with the resistive load is presented. [ABSTRACT FROM AUTHOR]

In the field of electromagnetic launch or other military research, the requirements for the power density of high-voltage capacitor charging power supply (CCPS) are increasing. The design of the cooling system becomes more difficult, especially in the intermittent operation mode, when the power supply exists transient heating process. As the main heating element of CCPS, the inverter unit is the key factor to influence the power density. In this paper, the main factors that influence the temperature rise of the device are analyzed, including the material and size of the heat sink. The rules between the above factors and the transient temperature rise are analyzed by Matlab simulation software. Then, the architecture model of inverter unit is established through ICEPAK software for simulation, which proves the accuracy of the regular. A basis for designing system level power supplies working in intermittent operating mode is provided through the transient thermal design of inverter unit’D The accuracy of the rule is verified through some load short circuit experiments with a 30-kW/6 kV charging power supply. [ABSTRACT FROM PUBLISHER]

During a disruption, plasma electromagnetic energy usually damages tokamak devices severely. Thus, this paper presents a five-part energy processing system (EPS) to dispose this energy. The five parts of the EPS are as follows: the metal oxide varistors employed to limit overvoltage and to absorb energy, the resistor module applied to consume energy, the pulse capacitor module used to store energy, the inverter module used for energy feedback, and the controller. These parts are described, and their key design features are introduced. The influence of different capacitances and resistances on the amount of energy transferred is investigated. The simulation results obtained by the Power Simulation program are given. The experimental and simulation results show that about 20%–30% of the total plasma electromagnetic energy can be transferred out of the tokamak device and effectively disposed by the EPS during the disruptions in the Joint Texas Experimental Tokamak (J-TEXT) tokamak. Moreover, the loop voltage during a disruption can be inhibited and decreases about 40%. [ABSTRACT FROM AUTHOR]

The acceleration grid power supply (AGPS) is an important part of the neutral beam injector (NBI) system. With the increase in NBI power, the requirement for output voltage of the AGPS is becoming higher and higher, even reaching to 1000 kV. As the inverter-type high voltage power supply uses inverters located at the lower voltage side to regulate and cut off the output voltage, it is very suitable for high-voltage applications. The proposed scheme for the AGPS of the International Thermonuclear Experimental Reactor (ITER) NBI system comprises five stages, where each stage has an inverter-type power supply with an output voltage of 200 kV. This paper investigates the inverter-type power supply based on neutral point clamped three-phase three-level (TPTL) inverter and three-phase step-up transformer, which is equivalent to an insulated TPTL dc–dc converter connected with a dual dc link. In order to design a preferable controller for the inverter-type power supply, the topology and principles of the TPTL dc–dc converter with duty cycle modulation have been analyzed. It indicates that only when the converter operates at a large duty cycle, the output voltage ripple can be limited to ±5%. Hence, the small signal model of the converter at a duty cycle larger than 2/3 is established. Following the mathematical model, a single-loop PID controller has been designed and a 400 V/6 A prototype has been built. Simulation and experimental results verify the correctness of the theoretical analysis. The system achieves a lower output voltage ripple and fast dynamic response. [ABSTRACT FROM AUTHOR]

Utilization of power electronics converters in pulsed power applications introduced a new series of reliable, long life, and cost-effective pulse generators. However, these converters suffer from the limited power ratings of semiconductor switches, which necessitate introduction of a new family of modular topologies. This paper proposes a modular power electronics converter based on voltage multiplier as a high voltage pulsed power generator. This modular circuit is able to generate flexible high output voltage from low input voltage sources. Circuit topology and operational principles of proposed topology are verified via experimental and simulation results as well as theoretical analysis. [ABSTRACT FROM PUBLISHER]

A new pulsed-power generator based on a Marx generator (MG) is proposed in this paper with a reduced number of semiconductor components and with a more efficient load-supplying process. The main idea is to charge two groups of capacitors in parallel through an inductor and take advantage of the resonant phenomenon in charging each capacitor up to twice as the input-voltage level. In each resonant half-cycle, one of those capacitor groups is charged; eventually, the charged capacitors will be connected in series, and the summation of the capacitor voltages are appeared at the output of a pulsed-power converter. This topology can be considered as a modified MG, which works based on the resonant concept. The simulated models of this converter have been investigated in a MATLAB/Simulink platform, and a laboratory prototype has been implemented in a laboratory. The simulation and test results verify the operation of the proposed topology in different switching modes. [ABSTRACT FROM AUTHOR]

This paper describes a concept and a physical demonstration of a high-efficiency small-size low-cost 100-kV 100-kW high-voltage (HV) power supply (HVPS) designed for long-pulse applications (units of milliseconds to dc operation). Key technology includes a modular HV converter with energy-dosing inverters that run at about 50 kHz and have demonstrated an efficiency of 97.5% across a wide range of operating conditions. The inverters' output voltages are phase shifted, which yields a low ripple of 1% and a slew rate of 3 \kV/\mu\s combined with less than 10 J of stored energy at the maximum voltage. Modular construction allows easy tailoring of HVPS for specific needs. Owing to high efficiency, small size is achieved without water cooling. Controls provide standard operating features and advanced digital processing capabilities, along with easiness of accommodating application-specific requirements. HVPS design and testing are detailed. It is shown that the ripple factor is inversely proportional to the number of modules squared. Experimental current and voltage waveforms indicate virtually lossless switching for widely varying load in the full range of the line input voltages and fair agreement with circuit simulations. The overall efficiency is as high as 95% at full load and greater than 90% at 20% load, with a power factor that is typically greater than 93%. [ABSTRACT FROM PUBLISHER]

A new method to suppress tearing mode and accelerate magnetic island rotation has been explored. To verify this method on the J-TEXT tokamak, a current-pulse power supply is designed to drive the resonant magnetic perturbation coils with a frequency range from 1 to 5 kHz and amplitude of 3 kA, which can create 0.75 G of magnetic perturbation. The current-pulse power supply topology is modified by H-bridge inverter, which can create a bipolar pulsed current. A set of boost capacitors with an isolation diode is added on dc bus just before the inverter. During the current changing time, the boost capacitors can store the energy of inductive load to steepen the current falling edge and create high voltage to accelerate the current rising speed. This modified topology has a rapid current changing edge and the wide range of operating frequency. A small power prototype is built to verify the topology. [ABSTRACT FROM AUTHOR]

When small currents are interrupted by a vacuum switch, it is well known that the chopping current and the associated overvoltage are observed. Many investigations on the current-chopping phenomena in alternating-current (ac) circuits have been carried out, but there are no data available on inverter circuits in spite of their recent wide application to synchronous motor systems. In this paper, chopping-current levels and the overvoltages in an inverter circuit under a simple three-level pulsewidth-modulated control are investigated. As a result, the mean chopping-current level is three to four times higher than that in an ac circuit. In particular, high chopping currents occur only when the timing of the current interruption by the vacuum switch synchronizes with that of the inverter's switching, which we call “double chopping.” High chopping current due to double chopping might be harmful since the high overvoltage proportional to the chopping-current level could damage the insulation of electric equipment. However, we experimentally confirmed that a typical surge suppressor could reduce overvoltage. [ABSTRACT FROM AUTHOR]

In this paper, a new dimmable electronic ballast for metal-halide (MH) lamps based on a three-stage structure is proposed. The presented dimmable electronic ballast can dim smoothly without acoustic resonance from 50% to 100% brightness. A novel current-control method with constant-power capability is also presented to solve the power-drifting problem resulting from the V– I characteristic variations between lamps or caused by the aging of lamp. The dimming capability allows the ballast to adjust its working condition according to the environments or the dimming command; this further improves the energy efficiency. Finally, a 150-W MH lamp ballast prototype is built to verify the feasibility of the proposed methods. [ABSTRACT FROM PUBLISHER]

A mercury-free flat fluorescent lamp with an arclike electrode is developed to improve luminance and luminous efficacy and to prevent discharge contraction. The influences of the rising time of a driving waveform and the gas mixture under different gas pressures on luminance and luminous efficacy are studied. The experimental results show that the luminance and luminous efficacy increase as the gas pressure and Xe content increase. The luminance of about 7500 \cd/\m^2 can be achieved at a pressure of 60 kPa with Ne–Xe (30%). The maximum luminous efficacy of the system, including the inverter, is about 23.7 lm/W at a pressure of 50 kPa with Ne–Xe (30%). Compared with the gas mixture of Ne–Xe (30%), when the gas mixture of Ne–Xe (32%)–He (8%) is used, the luminance and ignition voltage increase. In addition, the luminous efficacy for a steep rising edge of a waveform within 400 ns can be increased about 10% higher than that for a gradual rising edge above 800 ns. [ABSTRACT FROM PUBLISHER]

A 20-kJ/s 10-kV 1-kHz repetition rate capacitor charger design and testing are described. The goal of the development was to combine high performance and versatility with low-cost design and good manufacturability. This goal was met using an energy-dosing converter topology with smart controls adapting the switching frequency in such a way as to ensure zero-current switching for all possible scenarios, keeping maximum duty cycle for high power. The switching is accomplished at a frequency of up to 55 kHz, employing relatively slow insulated-gate bipolar transistors with low conduction losses. High efficiency allows all-air cooled design that fits into a 19^\prime\prime\times 10^\prime\prime\times 24^\prime\prime \ \rack. Design guidelines are reviewed. Comprehensive PSpice models accounting for numerous parasitic parameters and mimicking controls for the frequency variation were developed and simulation results are presented. Worst-case repeatability analysis has been performed. Both PSpice simulations and analytical tools predicted pulse-to-pulse repeatability of 0.3%; the measured figures are 0.8% and 1% for short- and long-term operations, respectively, at peak charging and repetition rates. Typical current and voltage traces and results of thermal runs are presented. [ABSTRACT FROM PUBLISHER]

An integrated full-bridge inverter circuit with fewer components and lower volume is proposed. The conventional light sintering system uses several independent power supplies, each having an input voltage source and inverting component. However, the structure of the proposed circuit comprises only one full-bridge inverter with two separated transformers for applying independent dc trigger and simmer output voltages. The separated transformers are considered to have the same operation switching frequency because of the integrated inverter part. When designing the system, we considered not only matching the switching frequency but also turning-on of the xenon flash lamp. Some of the considerations are as follows: no-load characteristic of the lamp at the initial moment, voltage-boosting effect of the parasitic inductance and capacitance, additional simmer output current path for continuous conduction, and dc trigger turn-off moment when the 15-kV trigger output voltage changes the lamp impedance. Here, the successful results of the aforementioned considerations for applying the light sintering technology are presented. The simulation and no-load experiment waveforms are consistent with the analysis of the effects of the parasitic inductance and capacitance. In addition, the waveforms show 15- and 1.0-kV stable output voltages for the dc trigger and simmer power supplies, respectively. Finally, the xenon flash lamp load is tested, and the integrated system is observed to be functional for single or series-connected lamps. [ABSTRACT FROM AUTHOR]

There is considerable need for a mobile, reliable, efficient, and compact prime power supply for a host of applications, including directed energy and electrical grid backup among others. Electrochemical energy storage devices, which possess either high-power density or high-energy density, have been developed recently and are very applicable for use in these applications. The need for both high energy and high power, however, makes the design and implementation of such a prime power supply a nontrivial task. While lithium-ion batteries (LIBs) are available, which possess both high power and energy density, operation at high power reduces their cycle life, decreasing the reliability and increasing the cost of the system when replacement becomes necessary more frequently. One proposed method involves optimally combining high-energy batteries with high-power electric double layer capacitors (EDLCs) using actively controlled power electronics to regulate the current to and from each respective device. In such a scheme, energy can be slowly sourced to and from the batteries, while the capacitors are used to supply or accept the bulk of the current when the demand is high, especially during fast transients. This type of scheme should not only maximize the batteries’ cycle life and ensure that both the energy and power required of the load(s) is always available, but will also increase the instantaneous power capabilities of the system, offering a well-rounded solution to sourcing steady and/or transient loads. When augmenting a fossil fuel generator with a hybrid energy storage module (HESM), the HESM has the ability to act as a high-energy reservoir that can harvest energy from the generator when the loads are in short periods of inactivity. This enables the generator to be continuously base loaded, thereby maintaining a high level of efficiency at all times, while theoretically maintaining the required power quality of the main ac bus. At the University of Texas at Arlington (UTA), an actively controlled, high-rate HESM has been constructed to evaluate its performance under the typical load condition presented by directed energy weapons. It has been assembled using LIBs, EDLCs, and commercial off-the-shelf power electronic converters. A discussion about the future of HESMs, the experimental setup at UTA, and the results obtained thus far will be presented here. [ABSTRACT FROM PUBLISHER]

This document reviews the current-mode supply approach for dielectric barrier discharge (DBD) excilamps. It briefly demonstrates why this mode assures the control of the power injected into the DBD. Considerations with the step-up transformer required for the correct operation of the current-mode are developed. This document shows and compares four different converter topologies that comply with this principle. This comparison is made in terms of electric efficiency and luminous efficacy using experimental measurements. [ABSTRACT FROM PUBLISHER]

Integrated circuits are inherently complicated and made more by increasing transistor quantity and density. This trend potentially enhances concomitant effects of high-energy ionizing radiation and local or impressed electromagnetic interference (EMI). The reduced margin for signal error may counter any gain in radiation hardness from smaller device dimensions. Isolated EMI and ionizing radiation studies on circuits have been extensively conducted over the past 30 years. However, little focus has been placed on the combined effects. To investigate the effect of combined EMI and ionizing radiation, two complementary metal–oxide–semiconductor inverter technologies (CD4069 and SN74AUC1G04) were analyzed for their static performance in response to both EMI and gamma radiation up to 132 krd(Si). The combined EMI and gamma radiation environment, compared to the isolated effects of each, produced the most severe degradation in inverter performance for both device technologies. [ABSTRACT FROM PUBLISHER]

Inductively coupled plasma source connected to a diffusion vacuum chamber is operated with an inverter-type radio frequency (RF) power supply in 10-Pa argon. Plasma structure in the glass source tube is preliminarily studied by acquisition of digital images. A RF antenna is powered with a frequency of \sim100~kHz , which is adjusted in order to optimize impedance matching condition. Near the RF antenna, the plasma production over the glass source tube diameter is observed, whereas the smaller diameter plasma transport and the stationary plasma striation structure are seen between the RF antenna and diffusion chamber. [ABSTRACT FROM PUBLISHER]