Papers by Henry Obermeyer
While the concept of pumped storage hydropower (PSH) is not new, adjustable-speed pumped storage ... more While the concept of pumped storage hydropower (PSH) is not new, adjustable-speed pumped storage hydropower (AS-PSH) is equipped with power electronics; thus, it has more capabilities and is more agile and flexible to integrate with modern power systems. The composition of power systems from a century ago consist mostly of conventional synchronous generators delivering power to customers via a unidirectional power flow. As the ratio of conventional power plants with synchronous generators to variable generation decreases with increasing penetrations of renewables, future power systems will be more dynamic. With fewer synchronous generators, the level of the rotating inertia within the power system decreases, and balancing variable generation and load in a condition with low rotating inertia is not easy. Fortunately, AS-PSH can provide a quick and flexible response with the power converter control while balancing the supply and demand, thus securing power system stability. In a way, AS-PSH is a combination of energy storage (storing potential energy) and a conventional power plant. This report covers the electrical systems of PSH plants, including the generator, the power converter, and the grid integration aspects. Future PSH will most likely be influenced by the technology (advancement of the electric machines, power converters, smart sensors, control systems, grid/microgrid configurations), the requirement and the need to maintain the reliability of power systems (grid code; local, regional, and environmental rules and regulations), the potential revenues from offering system reliability products (various ancillary services: ramping, reserves, inertial and frequency response; voltage and reactive power regulations), and energy arbitrage.
Toughness and intergranular fracture of a simulated carburized case in EX-24 type steel
Journal of heat treating, Jun 1, 1980
The high carbon case of a carburized steel has been simulated by producing EX-24 steel containing... more The high carbon case of a carburized steel has been simulated by producing EX-24 steel containing 0.85 pct C. Two heats, one containing 0.044 pct P and one containing 0.002 pct P, were examined. Specimens were austenitized between 760 and 1130 °C, oil quenched and tempered at 170 °C. The low P specimens always showed the best fracture toughness as measured by testing of precracked compact tension specimens. Intergranular fracture susceptibility, as determined by scanning electron microscopy, was increased by reduced rates of cooling during quenching, high austenitizing temperature, and high P content. Cooling experiments and A uger electron spectroscopy showed that the intergranular cracking was related to cementite formation at austenite grain boundaries during quenching. The cementite formation was in turn enhanced by P segregation to the austenite grain boundaries during austenitizing.
Frequency Support Enhancement of a Permanent Magnet-Based Adjustable-Speed Pumped Hydropower Plant
When a permanent magnet (PM) –based adjustable-speed pumped storage hydropower (AS-PSH) plant del... more When a permanent magnet (PM) –based adjustable-speed pumped storage hydropower (AS-PSH) plant delivers frequency response via the full-scaled power converter, there is power imbalance at the PM generator during the initial stage of the frequency response. This is because the AS-PSH has the different time constants between the power converter and wicket gate in the governor valve. Thus, this imbalance causes a sudden reduction of the rotational speed of the machine during the frequency response. As a result, a voltage deficit arises at the generator terminal in proportion to the decrement in the rotational speed, and thereby it is promising that the current flow at the converter will reach its limit when attempting to inject the commanded active power at a reduced voltage level. Thus, this causes the degradation of the frequency response of the AS-PSH due to the self-demagnetization at a reduced rotational speed. This paper proposes a frequency support scheme of a PM-based AS-PSH to enhance the frequency response by bridging the gap between the different time constants. To achieve this, the frequency support scheme includes a gate opening adjustment in the governor and a dynamic ramp-down in converter controller of the AS-PSH.
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Apr 12, 2022
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Aug 5, 2019
Department of Energy (DOE) reports produced after 1991 and a growing number of pre-1991 documents... more Department of Energy (DOE) reports produced after 1991 and a growing number of pre-1991 documents are available free via www.OSTI.gov.
U.S. Department of Energy Office of Scientific and Technical Information - OSTI OAI, Aug 5, 2019
Department of Energy (DOE) reports produced after 1991 and a growing number of pre-1991 documents... more Department of Energy (DOE) reports produced after 1991 and a growing number of pre-1991 documents are available free via www.OSTI.gov.
Spectrometric synthetic aperture radar
U.S. Department of Energy Office of Scientific and Technical Information - OSTI OAI, Oct 21, 2019
Department of Energy (DOE) reports produced after 1991 and a growing number of pre-1991 documents... more Department of Energy (DOE) reports produced after 1991 and a growing number of pre-1991 documents are available free via www.OSTI.gov.
Systeme d'assemblage haute tenue pour des materiaux composites a fibres
La presente invention a trait a l'assemblage de structures a base de materiaux composites a f... more La presente invention a trait a l'assemblage de structures a base de materiaux composites a fibres avec une continuite du renfort de fibres a travers tous les bords entre la colle et le substrat. Un controle de gradient thermique de l'etendue de l'infusion des resines ou de substances de blocage de resines, lors de la fabrication de composants a etre ulterieurement lies, fournit des fibres de renfort partiellement exposees qui servent au renfort d'un joint ou bord forme ulterieurement.
Established methods for design and construction of steel reinforced concrete structures universal... more Established methods for design and construction of steel reinforced concrete structures universally utilize continuous reinforcement through all tensile load carrying joints. This stands in sharp contrast to current practice in the field of fiber reinforced composites, which relies almost exclusively on adhesively bonded joints or discrete fasteners. These bonding techniques entirely lack fiber continuity between primary fiber reinforced components and result in inherently low joint efficiency. Techniques for providing controlled zones of non-resininfused “dry fiber”, for incorporation into fully reinforced secondary operation joints, have been investigated. Load paths, applications and techniques for both prepreg structures and resin transfer molded structures are outlined.
Manette a axes multiples et moyen transducteur associe
L'invention porte sur des manettes a axes multiples ameliorees et sur des moyens de mesure de... more L'invention porte sur des manettes a axes multiples ameliorees et sur des moyens de mesure de deplacement optique a axes multiples associes. Ces moyens de mesure de deplacement comprennent au moins un emetteur de lumiere (4) et au moins un detecteur de lumiere (5a-5f), de preference places sur un reseau hexagonal plat. La position relative d'un bloc reflecteur mobile adjacent (2a-2f) peut etre mesuree selon une amplitude de six degres grâce aux variations de l'amplitude lumineuse detectee. Differentes configurations ergonomiques de modes de realisation de manettes a six axes peuvent etre facilitees par la conception compacte du moyen transducteur. L'invention porte aussi sur un moyen de regler de maniere dynamique les transformations cordonnees pour le controle de la machinerie de construction.
Vanne de garde d'eau et actionneur correspondant
Cette invention porte sur des vannes de garde d'eau perfectionnees et sur les actionneurs gon... more Cette invention porte sur des vannes de garde d'eau perfectionnees et sur les actionneurs gonflables correspondants, ainsi que sur des appareils et des procedes associes d'etancheite, de fabrication et de fonctionnement. Cette invention porte egalement sur les progres realises dans les technologies en matiere, notamment, de conception d'admission d'air, de reduction des tensions exercees sur les sacs gonfles, d'augmentation de la resistance des sacs gonflables, de reduction des frictions de coulissement associees a une vanne d'eau, de butee et autres joints d'etancheite d'eau de retenue, de fabrication de panneaux de vanne, de structures de retenue d'eau permettant la circulation et d'efficacite de fonctionnement des systemes a panneaux de vanne d'eau, ainsi que concernant l'aeration de lames d'eau, les charnieres et la technologie de fabrication de sacs.
Multi-Axis Input Apparatus
Process of manufacturing fiber reinforced composite via selective infusion of resin and resin blocking substance
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Papers by Henry Obermeyer