Power conversion technologies

The mission of the Engineering Research, Development, and Technology Program at Lawrence Livermore National Laboratory (LLNL) is to develop the knowledge base, process technologies, specialized equipment, tools and facilities to support current and future LLNL programs. Engineering`s efforts are guided by a strategy that results in dual benefit: first, in support of Department of Energy missions, such as national security through nuclear deterrence; and second, in enhancing the nation`s economic competitiveness through our collaboration with U.S. industry in pursuit of the most cost- effective engineering solutions to LLNL programs. To accomplish this mission, the Engineering Research, Development, and Technology Program has two important goals: (1) identify key technologies relevant to LLNL programs where we can establish unique competencies, and (2) conduct high-quality research and development to enhance our capabilities and establish ourselves as the world leaders in these technologies. To focus Engineering`s efforts technology {ital thrust areas} are identified and technical leaders are selected for each area. The thrust areas are comprised of integrated engineering activities, staffed by personnel from the nine electronics and mechanical engineering divisions, and from other LLNL organizations. This annual report, organized by thrust area, describes Engineering`s activities for fiscal year 1996. The report provides timely summaries of objectives, methods, and key results from eight thrust areas: Computational Electronics and Electromagnetics; Computational Mechanics; Microtechnology; Manufacturing Technology; Materials Science and Engineering; Power Conversion Technologies; Nondestructive Evaluation; and Information Engineering. Readers desiring more information are encouraged to contact the individual thrust area leaders or authors. 198 refs., 206 figs., 16 tabs.

From its founding in 1952 until today, Lawrence Livermore National Laboratory (LLNL) has made significant strategic investments to develop high performance computing (HPC) and its application to national security and basic science. Now, 60 years later, the Computation Directorate and its myriad resources and capabilities have become a key enabler for LLNL programs and an integral part of the effort to support our nation's nuclear deterrent and, more broadly, national security. In addition, the technological innovation HPC makes possible is seen as vital to the nation's economic vitality. LLNL, along with other national laboratories, is working to make supercomputing capabilities and expertise available to industry to boost the nation's global competitiveness. LLNL is on the brink of an exciting milestone with the 2012 deployment of Sequoia, the National Nuclear Security Administration's (NNSA's) 20-petaFLOP/s resource that will apply uncertainty quantification to weapons science. Sequoia will bring LLNL's total computing power to more than 23 petaFLOP/s-all brought to bear on basic science and national security needs. The computing systems at LLNL provide game-changing capabilities. Sequoia and other next-generation platforms will enable predictive simulation in the coming decade and leverage industry trends, such as massively parallel and multicore processors, to run petascale applications. Efficient petascale computing necessitates refining accuracy in materials property data, improving models for known physical processes, identifying and then modeling for missing physics, quantifying uncertainty, and enhancing the performance of complex models and algorithms in macroscale simulation codes. Nearly 15 years ago, NNSA's Accelerated Strategic Computing Initiative (ASCI), now called the Advanced Simulation and Computing (ASC) Program, was the critical element needed to shift from test-based confidence to science-based confidence. Specifically, ASCI/ASC accelerated the development of simulation capabilities necessary to ensure confidence in the nuclear stockpile-far exceeding what might have been achieved in the absence of a focused initiative. While stockpile stewardship research pushed LLNL scientists to develop new computer codes, better simulation methods, and improved visualization technologies, this work also stimulated the exploration of HPC applications beyond the standard sponsor base. As LLNL advances to a petascale platform and pursues exascale computing (1,000 times faster than Sequoia), ASC will be paramount to achieving predictive simulation and uncertainty quantification. Predictive simulation and quantifying the uncertainty of numerical predictions where little-to-no data exists demands exascale computing and represents an expanding area of scientific research important not only to nuclear weapons, but to nuclear attribution, nuclear reactor design, and understanding global climate issues, among other fields. Aside from these lofty goals and challenges, computing at LLNL is anything but 'business as usual.' International competition in supercomputing is nothing new, but the HPC community is now operating in an expanded, more aggressive climate of global competitiveness. More countries understand how science and technology research and development are inextricably linked to economic prosperity, and they are aggressively pursuing ways to integrate HPC technologies into their native industrial and consumer products. In the interest of the nation's economic security and the science and technology that underpins it, LLNL is expanding its portfolio and forging new collaborations. We must ensure that HPC remains an asymmetric engine of innovation for the Laboratory and for the U.S. and, in doing so, protect our research and development dynamism and the prosperity it makes possible. One untapped area of opportunity LLNL is pursuing is to help U.S. industry understand how supercomputing can benefit their business. Industrial investment in HPC applications has historically been limited by the prohibitive cost of entry, the inaccessibility of software to run the powerful systems, and the years it takes to grow the expertise to develop codes and run them in an optimal way. LLNL is helping industry better compete in the global market place by providing access to some of the world's most powerful computing systems, the tools to run them, and the experts who are adept at using them. Our scientists are collaborating side by side with industrial partners to develop solutions to some of industry's toughest problems. The goal of the Livermore Valley Open Campus High Performance Computing Innovation Center is to allow American industry the opportunity to harness the power of supercomputing by leveraging the scientific and computational expertise at LLNL in order to gain a competitive advantage in the global economy.

The Multiscale Epidemiologic/Economic Simulation and Analysis (MESA) Decision Support System (DSS) is the product of investments that began in FY05 by the Department of Homeland Security (DHS) Science and Technology Directorate and continue today with joint funding by both DHS and the US Department of Agriculture (USDA). The DSS consists of a coupled epidemiologic/economic model, a standalone graphical user interface (GUI) that supports both model setup and post-analysis, and a Scenario Bank archive to store all content related to foreign animal disease (FAD) studies. The MESA epi model is an object-oriented, agent-based, stochastic, spatio-temporal simulator that parametrically models FAD outbreaks and response strategies from initial disease introduction to conclusion over local, regional, and national scales. Through its output database, the epi model couples to an economic model that calculates farm-level impacts from animal infections, responsive control strategies and loss of trade. The MESA architecture contains a variety of internal models that implement the major components of the epi simulation, including disease introduction, intra-herd spread, inter-herd spread (direct and indirect), detection, and various control strategies (movement restrictions, culling, vaccination) in a highly configurable and extensible fashion. MESA development was originally focused to support investigations into the economic and agricultural industry impacts associated with Foot-and-Mouth Disease (FMD outbreaks). However, it has been adapted to other FADs such has Highly Pathogenic Avian Influenza (HPAI), Classical Swine Fever (CSF) and Exotic Newcastle Disease (END). The MESA model is highly parameterized and employs an extensible architecture that permits straightforward addition of new component models (e.g., alternative disease spread approaches) when necessary. Since its inception, MESA has been developed with a requirement to enable simulation of the very large scale, nationwide disease outbreaks that are of special interest to DHS. MESA has been developed at Lawrence Livermore National Laboratory (LLNL) and has benefited from the world-class experience in supercomputing application development held by LLNL staff as well as the best-in-class high performance computing infrastructure in place at LLNL. MESA incorporates novel architectural features that permit it to make efficient use of available compute cycles by dynamically increasing the fidelity of the simulation in spatial (geopolitical) regions where relevant activity is occurring and keeping other regions aggregated into a computationally simpler representation. In addition to the MESA epi and economic models, the MESA DSS incorporates other key components. Integral to the parametric approach MESA employs to setup and define disease outbreak scenarios is a GUI that enables the MESA user to efficiently manage the thousands of parameters required by the simulator. The GUI provides individual parameter editors for groups of variables that support a common high level function, such as disease introduction, spread, control strategies, etc. It also provides a capability to browse through multiple study projects and develop n-additional outbreak scenarios per project through successive refinement of existing scenarios. Finally, the MESA GUI links post-processing applications that permit extraction of key data from MESA raw output, generation of spreadsheets, and geospatial mapping of simulation results. The MESA GUI is a standalone application that normally runs on the user's desktop, although its Java source code is portable and can execute under virtually any modern operating system. The final major component of the MESA DSS is the Scenario Bank, which is a web-served archive of unclassified FAD study content. The Scenario Bank implements a hierarchy of spaces, structured primarily along organizational lines (e.g., 'USDA', 'LLNL', etc), that permits participants to store simulator inputs, outputs, analysis results, reports, etc. and explicitly control who among Bank users may access them. Documents can be shared within organizations or across organizations at the owner's discretion. The Scenario Bank is intended to be the system of record for USDA and DHS sponsored FAD study efforts and as such will archive content from a variety of models employed by USDA and DHS-sponsored researchers and analysts.

The Fast Ignition (FI) Concept for Inertial Confinement Fusion (ICF) has the potential to provide a significant advance in the technical attractiveness of Inertial Fusion Energy reactors. FI differs from conventional “central hot spot” (CHS) target ignition by decoupling compression from heating: using a laser (or heavy ion beam or Z pinch) drive pulse (10’s of nanoseconds) to create a dense fuel and a second, much shorter (~10 picoseconds) high intensity pulse to ignite a small volume within the dense fuel. The physics of fast ignition process was the focus of our Advanced Concept Exploration (ACE) program. Ignition depends critically on two major issues involving Relativistic High Energy Density (RHED) physics: The laser-induced creation of fast electrons and their propagation in high-density plasmas. Our program has developed new experimental platforms, diagnostic packages, computer modeling analyses, and taken advantage of the increasing energy available at laser facilities to advance understanding of the fundamental physics underlying these issues. Our program had three thrust areas: • Understand the production and characteristics of fast electrons resulting from FI relevant laser-plasma interactions and their dependence on laser prepulse and laser pulse length. • Investigate the subsequent fast electron transport in solid and through hot (FI-relevant) plasmas. • Conduct and understand integrated core-heating experiments by comparison to simulations. Over the whole period of this project (three years for this contract), we have greatly advanced our fundamental understanding of the underlying properties in all three areas: • Comprehensive studies on fast electron source characteristics have shown that they are controlled by the laser intensity distribution and the topology and plasma density gradient. Laser pre-pulse induced pre-plasma in front of a solid surface results in increased stand-off distances from the electron origin to the high density target as well as large and erratic spread of the electron beam with increasing short pulse duration. We have demonstrated, using newly available higher contrast lasers, an improved energy coupling, painting a promising picture for FI feasibility. • Our detailed experiments and analyses of fast electron transport dependence on target material have shown that it is feasible to collimate fast electron beam by self-generated resistive magnetic fields in engineered targets with a rather simple geometry. Stable and collimated electron beam with spot size as small as 50-μm after >100-μm propagation distance (an angular divergence angle of 20°!) in solid density plasma targets has been demonstrated with FI-relevant (10-ps, >1-kJ) laser pulses Such collimated beam would meet the required heating beam size for FI. • Our new experimental platforms developed for the OMEGA laser (i.e., i) high resolution 8 keV backlighter platform for cone-in-shell implosion and ii) the 8 keV imaging with Cu-doped shell targets for detailed transport characterization) have enabled us to experimentally confirm fuel assembly from cone-in-shell implosion with record-high areal density. We have also made the first direct measurement of fast electron transport and spatial energy deposition in integrated FI experiments enabling the first experiment-based benchmarking of integrated simulation codes. Executing this program required a large team. It was managed as a collaboration between General Atomics (GA), Lawrence Livermore National Laboratory (LLNL), and the Laboratory for Laser Energetics (LLE). GA fulfills its responsibilities jointly with the University of California, San Diego (UCSD), The Ohio State University (OSU) and the University of Nevada at Reno (UNR). The division of responsibility was as follows: (1) LLE had primary leadership for channeling studies and the integrated energy transfer, (2) LLNL led the development of measurement methods, analysis, and deployment of diagnostics, and (3) GA together with UCSD, OSU and UNR studied the detailed energy-transfer physics. The experimental program was carried out using the Titan laser at the Jupiter Laser Facility at LLNL, the OMEGA and OMEGA EP lasers at LLE and the Texas Petawatt laser at the University of Texas, Austin. Modeling has been pursued on large computing facilities at LLNL, OSU, and UCSD using codes developed (by us and others) within the HEDLP program, commercial codes, and by leveraging existing simulations codes developed by the National Nuclear Security Administration ICF program. One important aspect of this program was the involvement and training of young scientists including postdoctoral fellows and graduate students. This project generated an impressive forty articles in high quality journals including nine (two under review) in Physical Review Letters during the three years of this grant and five graduate students completed their doctoral dissertations.

The mission of the Engineering Research, Development, and Technology Program at Lawrence Livermore National Laboratory (LLNL) is to develop the technical staff, tools, and facilities needed to support current and future LLNL programs. The efforts are guided by a dual-benefit research and development strategy that supports Department of Energy missions, such as national security through nuclear deterrence and economic competitiveness through partnerships with U.S. industry. This annual report, organized by thrust area, describes the activities for the fiscal year 1993. The report provides timely summaries of objectives, methods, and results from nine thrust areas for this fiscal year: Computational Electronics and Electromagnetics; Computational Mechanics; Diagnostics and Microelectronics; Fabrication Technology; Materials Science and Engineering; Power Conversion Technologies; Nondestructive Evaluation; Remote Sensing, Imaging, and Signal Engineering; and Emerging Technologies. Separate abstracts were prepared for 47 papers in this report.

A novel high frequency high voltage (HV) generator circuit with air-core transformer is proposed in this paper to achieve high power density packaging structure and compact size advantages. Planar multi-layer printed circuit board(PCB) winding and litz wire wound winding structure are investigated for air-core HV transformer. The electrical design of air-core HV transformer with HV multiplier circuit based on 1.2kV SiC Schottky diode are introduced. A with 450 kHz switching frequency HV generator prototype with 310W output power and 1kV output voltage is built in lab. The litz wire air-core HV transformer prototype is built to compare the efficiency, thermal performance and size with planar air-core HV transformer. The planar PCB air-core transformer based on HV generator can achieve 80.5% efficiency and 1.09kW/L power density. The litz wire wounded transformer based HV generator provide 89.0% efficiency and around 0.53kW/L power density. The design with planar PCB air-core transformer enable high voltage generation circuit system compact planar packaging. The design with litz wire air-core HV transformer behaves higher efficiency and thermal performance with low high frequency AC winding loss.

The National Ignition Facility (NIF) and Photon Science Directorate at Lawrence Livermore National Laboratory (LLNL) has substantial relevant experience in the construction of high energy lasers, and more recently in the development of advanced high average power solid state lasers. We are currently developing new concepts for advanced solid state laser drivers for the Laser Inertial Fusion Energy (LIFE) application, and other high average power laser applications that could become central technologies for use in space debris removal. The debris population most readily addressed by our laser technology is that of 0.1-10 cm sized debris in low earth orbit (LEO). In this application, a ground based laser system would engage an orbiting target and slow it down by ablating material from its surface which leads to reentry into the atmosphere, as proposed by NASA's ORION Project. The ORION concept of operations (CONOPS) is also described in general terms by Phipps. Key aspects of this approach include the need for high irradiance on target, 10{sup 8} to 10{sup 9} W/cm{sup 2}, which favors short (i.e., picoseconds to nanoseconds) laser pulse durations and high energy per pulse ({approx} > 10 kJ). Due to the target's orbital velocity, the potential duration of engagement is only of order 100 seconds, so a high pulse repetition rate is also essential. The laser technology needed for this application did not exist when ORION was first proposed, but today, a unique combination of emerging technologies could create a path to enable deployment in the near future. Our concepts for the laser system architecture are an extension of what was developed for the National Ignition Facility (NIF), combined with high repetition rate laser technology developed for Inertial Fusion Energy (IFE), and heat capacity laser technology developed for military applications. The 'front-end' seed pulse generator would be fiber-optics based, and would generate a temporally, and spectrally tailored pulse designed for high transmission through the atmosphere, as well as efficient ablative coupling to the target. The main amplifier would use either diode-pumped or flashlamp-pumped solid state gain media, depending on budget constraints of the project. A continuously operating system would use the gas-cooled amplifier technology developed for Mercury, while a burst-mode option would use the heat capacity laser technology. The ground-based system that we propose is capable of rapid engagement of targets whose orbits cross over the site, with potential for kill on a single pass. Very little target mass is ablated per pulse so the potential to create additional hazardous orbiting debris is minimal. Our cost estimates range from $2500 to $5000 per J depending on choices for laser gain medium, amplifier pump source, and thermal management method. A flashlamp-pumped, Nd:glass heat-capacity laser operating in the burst mode would have costs at the lower end of this spectrum and would suffice to demonstrate the efficacy of this approach as a prototype system. A diode-pumped, gas-cooled laser would have higher costs but could be operated continuously, and might be desirable for more demanding mission needs. Maneuverability can be incorporated in the system design if the additional cost is deemed acceptable. The laser system would need to be coupled with a target pointing and tracking telescope with guide-star-like wavefront correction capability.

Apart from the breaking and transferring devices, all other power quality (PQ) enhancement devices like DSTATCOM, DVR, UPQC etc. are based on power converters. Furthermore modern FACTS devices like STATCOM, SSSC, UPFC etc. also employ power converters. However, FACTS devices have much higher power rating than PQ enhancement devices since they are used in bulk power transmission systems. Moreover, their operation philosophy is also different as they are assumed to work under balanced sinusoidal conditions. As a consequence, the control strategies of FACTS devices are different from the PQ enhancement or Custom Power devices. Since power converters have an important role to play in modern power systems, we discuss their topologies and control strategies in this chapter. For the background materials in the area of Power Electronics, there are numerous excellent textbooks, e.g., [1, 2, 3].

A novel modular high frequency high voltage (HV) generator with silicon carbide (SiC) power semiconductor devices is proposed in this paper to achieve high efficiency, sharp HV pulse and compact size. The modular architecture is introduced for high frequency operation firstly. The switching characteristics and detailed design consideration on the gate driver circuit are given. Finally, the 8kW output-power, 110kV output-voltage HV generator prototype with 300 kHz~500 kHz switching frequency is built to validate the design. Compared with existing design, 2 times high power density, around 10% higher efficiency and 4 times faster HV pulse can be achieved from the proposed modular SiC HV generators.

In the JEM-EUSO focal instrument four multianode photomultipliers (Elementary Cell unit) are powered by one high voltage generator. The HV control system for Photo Detection Module consists of 9 high voltage generators. HV generators are Cockcroft-Walton voltage multipliers with protection system and with 3 level very fast switches for HV at cathodes. Protection systems were made to protect HVPS itself against possible excess of power consumption, but might be as well used as a protection of PMTs in case of unexpected enlighting. Externally controlled switches can reduce 100 times or 10000 times the PMT collection efficiency to enlarge the PMT dynamics up to factor 10 6 . The HV control unit provides galvanic insulation of HV system, and allows for input voltage in a range 15-35 V. Control unit provides interface for external voltage setting, control of switches, and emits information about the statuses of 9 HV generators.

There are several advantages of High voltage DC (HVDC) system. However, the main limitation of the HVDC system is the generation of HVDC. Therefore, the objective of the paper is to emphasize the design of a high voltage generation through Cockcroft–Walton Voltage multiplier circuit. This paper focus on development in Cockcroft-Walton Voltage multiplier circuit since decades, various other topologies available, designing parameters of Cockcroft–Walton Voltage multiplier circuit. The paper tends to explain the working of Cockcroft–Walton Voltage multiplier circuit for high voltage generation. With literature analysis operation of Cockcroft–Walton Voltage multiplier circuit is explained here and being a review paper, it does not include detailed explanation but the content of the paper is enough to understand the topologies, terminologies and parameters of designing the circuit.

This paper presents a high voltage generator utilizing a single piezoelectric element (PZT, 5 mm in diameter, 740 μm thick) with electrodes series-connected via a flexible Kapton cable. High voltage pulses over 1 kV are generated in response to transient mechanical input loads. The response of high voltage generator is evaluated for stress range from 1 MPa to 5 MPa. The high voltage generator is successfully used to operate a microdischarge-based chemical vapor sensor by providing high voltage pulses to enable microdischarge sparks across a 75 μm anode-cathode gap.

This paper presents high voltage generator for stun gun applications. The proposed high voltage generator consists of coupled-inductor boost and flyback converters, which adopts active clamp circuit to recover energy trapped in leakage inductances of coupled inductor and transformer in two converters simultaneously. With this approach, coupled-inductor boost converter can boost voltage of battery up to a high output voltage, while flyback converter is adopted to step up the output voltage up to the desired voltage of capacitated paralysis for convicts conferring. In order to increase safety of the stun gun, transformer of flyback with a high turns ratio is used by multi-winding method in secondary winding to speed up output response and to reduce charges supplied by stun gun for meeting maximum enduring charges of human body. Since switches in the proposed generator adopts switch integration technique, its weight and volume can be reduced and its conversion efficiency can be increased. As compared with conventional stun gun, the proposed one can achieve 210 ten-second firings which exceeds 1.5 times of ten-second firings of the conventional one. Finally, a prototype under maximum output voltage of 30kV and maximum output current of 5mA has been implemented to verify feasibility of the proposed high voltage generator.

Ultra high voltage STEM has many inherent technical advantages over CTEM. These advantages include better signal detectability and signal processing capability. It is hoped that it will explore some new applications which were previously not possible. Conventional STEM (including CTEM with STEM attachment), however, has been unable to provide these inherent advantages due to insufficient performance and engineering problems. Recently we have developed a new 1250 kV STEM and completed installation at Nagoya University in Japan. It has been designed to break through conventional engineering limitations and bring about theoretical advantage in practical applications.In the design of this instrument, we exercised maximum care in providing a stable electron probe. A high voltage generator and an accelerator are housed in two separate pressure vessels and they are connected with a high voltage resistor cable.(Fig. 1) This design minimized induction generated from the high voltage generator, which is a high frequency Cockcroft-Walton type, being transmitted to the electron probe.

Electrical Phenomena During Freezing of Water and Soils reviews the early observations of the generation of charges and electrical potentials developed during freezing of water, dilute aqueous solutions, and moist soils. Beginning with a description of the early observations of natural phenomena, such as lightning and thunderstorms, and the effects of these on aircraft flying through thunderclouds, the book describes the early laboratory measurements carried out to understand the physical processes behind charge separation and generation of high voltages at the freezing interface. The review concludes with examples of field studies and proposes the need to continue the studies to use the method as a geophysical tool to study the freezing of ground in cold regions.