Engineering topics
Liu, Bo
Publications and source records attributed to Liu, Bo.
Robust Matrix Completion State Estimation in Distribution Systems
Due to the insufficient measurements in the distribution system state estimation (DSSE), full observability and redundant measurements are difficult to achieve without using the pseudo measurements. The matrix completion state estimation (MCSE) combines the matrix completion and power system model to estimate voltage by exploring the low-rank characteristics of the matrix. This paper proposes a robust matrix completion state estimation (RMCSE) to estimate the voltage in a distribution system under a low-observability condition. Tradition state estimation weighted least squares (WLS) method requires full observability to calculate the states and needs redundant measurements to proceed a bad data detection. The proposed method improves the robustness of the MCSE to bad data by minimizing the rank of the matrix and measurements residual with different weights. It can estimate the system state in a low-observability system and has robust estimates without the bad data detection process in the face of multiple bad data. The method is numerically evaluated on the IEEE 33-node radial distribution system. The estimation performance and robustness of RMCSE are compared with the WLS with the largest normalized residual bad data identification (WLS-LNR), and the MCSE.
Robust Matrix Completion State Estimation in Distribution Systems: Preprint
Due to the insufficient measurements in the distribution system state estimation (DSSE), full observability and redundant measurements are difficult to achieve without using the pseudo measurements. The matrix completion state estimation (MCSE) combines the matrix completion and power system model to estimate voltage by exploring the low-rank characteristics of the matrix. This paper proposes a robust matrix completion state estimation (RMCSE) to estimate the voltage in a distribution system under a low-observability condition. Tradition state estimation weighted least squares (WLS) method requires full observability to calculate the states and needs redundant measurements to proceed a bad data detection. The proposed method improves the robustness of the MCSE to bad data by minimizing the rank of the matrix and measurements residual with different weights. It can estimate the system state in a low-observability system and has robust estimates without the bad data detection process in the face of multiple bad data. The method is numerically evaluated on the IEEE 33-node radial distribution system. The estimation performance and robustness of RMCSE are compared with the WLS with the largest normalized residual bad data identification (WLS-LNR), and the MCSE.
Growth of Single Crystal Fiber
Presented by NETL at 6th Workshop on Specialty Optical Fibers, 11/19
Synergistic Doping and Intercalation: Realizing Deep Phase Modulation on MoS 2 Arrays for High-Efficiency Hydrogen Evolution Reaction
A synergistic N doping plus PO 4 3- intercalation strategy is used to induce high conversion (ca. 41%) of 2H-MoS 2 into 1T-MoS, which is much higher than single N doping (ca. 28 %) or single PO 4 3- intercalation ca. 10%). A scattering mechanism is proposed to illustrate the synergistic phase transformation from the 2H to the 1T phase, which was confirmed by synchrotron radiation and.spherical aberration TEM. To further enhance reaction kindies, the designed (N, PO 4 3- )-MoS 2 nanosheds are combined with conductive vertical graphene (VG) skeleton forming binder-free arrays fir high efficiencyhydrogen evolution reaction (HER). Owing 10 the decreased band gap, lower d-band censer, and smaller hydrogen adsorption/desorption energy, the designed (NPO 4 3- )-MoSJVG electrode shows excellent HER perfor mance with a lower Tafel slope and overpotential than N-MoS 2 /VG, PO 4 3- -MoS 2 /VG counterparts, and other Mo-base catalysts in the literature.
Pressure-induced isostructural phase transition in [alpha]-Ni(OH)[subscript ]2 nanowires
Abstract not provided
Study of Melting Zone Profile and Defect Formation during Laser Heated Pedestal Growth
Presented by NETL at SPIE Defense & Commercial Sensing, 04/19
Precision Higgs physics at the CEPC
The discovery of the Higgs boson with its mass around 125 GeV by the ATLAS and CMS Collaborations marked the beginning of a new era in high energy physics. The Higgs boson will be the subject of extensive studies of the ongoing LHC program. At the same time, lepton collider based Higgs factories have been proposed as a possible next step beyond the LHC, with its main goal to precisely measure the properties of the Higgs boson and probe potential new physics associated with the Higgs boson. The Circular Electron Positron Collider~(CEPC) is one of such proposed Higgs factories. The CEPC is an $e^+e^-$ circular collider proposed by and to be hosted in China. Located in a tunnel of approximately 100~km in circumference, it will operate at a center-of-mass energy of 240~GeV as the Higgs factory. In this paper, we present the first estimates on the precision of the Higgs boson property measurements achievable at the CEPC and discuss implications of these measurements.
A Simple Control to Reduce Device Over-Voltage Caused by Non-Active Switch Loop in Three-Level ANPC Converters
With the development of wide band-gap (WBG) technology, the switching speed of power semiconductor devices increases, which makes circuits more sensitive to parasitics. For three-level active neutral point clamped (3L-ANPC) converters, the over-voltage caused by additional non-active switch loop can be an issue. This paper analyzes the multiple commutation loops in 3L-ANPC converter and summarizes the impact factors of the device over-voltage. The nonlinearity of the output capacitance of the device can significantly influence the over-voltage. A simple control without introducing additional hardware circuit or complex software algorithm is proposed to attenuate the effect of the nonlinear output capacitance. Multi-pulse test is conducted for a 3L-ANPC converter built with silicon carbide (SiC) MOSFETs. With the proposed control, the testing results show that the peak drain-source voltage of both active and non-active switches is reduced by more than 20% compared to the conventional control.
Reaction Mechanisms for Long-Life Rechargeable Zn/MnO 2 Batteries
Rechargeable aqueous Zn-ion batteries (ZIBs) are very promising for large-scale grid energy storage applications owing to their low cost, environmentally benign constituents, excellent safety, and relatively high energy density. Their usage, however, is largely hampered by the fast capacity fade. The complexity of the reactions has resulted in long-standing ambiguities of the chemical pathways of Zn/MnO 2 system. In this study, we find that both H + /Zn 2+ intercalation and conversion reactions occur at different voltages and that the rapid capacity fading can clearly be ascribed to the rate-limiting and irreversible conversion reactions at a lower voltage. By limiting the irreversible conversion reactions at ~1.26 V, we successfully demonstrate ultrahigh power and long life that are superior to most of the reported ZIBs or even some lithium-ion batteries.
Hidden Moving Target Defense against False Data Injection in Distribution Network Reconfiguration
This paper introduces Moving Target Defense (MTD) in distribution system against False Data Injection (FDI) attacks on the supervisory control and data acquisition (SCADA) system. Based on the AC power flow model, a hidden MTD (HMTD) strategy is constructed in combination with network reconfiguration by minimizing the system loss and line power flow differences before and after the HMTD. The proposed HMTD-based network reconfiguration is formulated as a mixed-integer nonlinear programming (MINLP) problem. A refined Genetic Algorithm (GA) is proposed to solve it. Numerical test is conducted in a modified IEEE-66 bus system. The simulation results show that the proposed model reduces the power loss introduced by the HMTD as well as yields a stealthy MTD to the attackers. The impact of HMTD on the system performance is also compared with that of the existing MTD strategies.
Stable, narrow spectral linewidth, fiber-delivered laser source for spin exchange optical pumping
Disclosed herein are example embodiments for providing high power, narrow linewidth, high-stability laser sources. Particular embodiments are adapted for use in spin exchange optical pumping (SEOP). One example system comprises an array of laser diodes; a beam twister positioned to receive individual beamlets from the array of laser diodes, the beam twister being configured to rotate the individual beamlets from the array of laser diodes and produce rotated beamlets; one or more collimating lenses positioned to receive the rotated beamlets produced by the beam twister and produce substantially collimated beamlets having a divergence angle; a spectral-line-width-reducing element positioned to receive the substantially collimated beamlets from the one or more collimating lenses and produce spectral-line-width-reduced beamlets; an optical fiber; and one or more focusing lenses positioned between the optical fiber and the spectral-line-width-reducing element and configured to receive the spectral-line-width-reduced beamlets and focus them into the optical fiber.
Optimization of crystal growth and properties of γ-CuI ultrafast scintillator by the addition of LiI
Highlights: • Large and transparent γ-CuI single crystal with the size over 20 mm was successfully obtained for the first time. • The intensities of near-band-edge emissions of γ-CuI single crystal are greatly enhanced by Li and I dopants. • The 430 nm emission decay time is less than 450 ps under pulsed X-ray irradiation. - Abstract: Large-sized γ-CuI single crystals with ultrafast scintillation property were grown in LiI acetonitrile solvent through evaporation technique. The LiI exhibits unique properties to γ-CuI single crystal preparation. One is that it increases the solubility of CuI in the solvent, which gives rise to a largest-sized (23 × 14 × 2 mm{sup 3}) single crystal with the high optical transmission (over 60%) in the wavelength region of 435–800 nm. The other feature is that it acts as an effective isoelectronic dopant and improves the molar ratio of copper to iodine, which greatly enhances the near-band-edge emissions (411 and 432 nm) and suppresses the broadband emission (680 nm). The decay time of the fast emission under pulsed X-ray excitation is shorter than 450 ps. The results will give a guidance for optimizing the properties of γ-CuI single crystal as an ultrafast scintillator.
Design and Implementation of Distributed Ultra-High Temperature Sensing System With a Single Crystal Fiber
Modern high-temperature processes, such as fossil energy production, nuclear reactors, and chemical reactors lack robust, distributed sensing systems to map temperatures in these high-value harsh-environment systems. Regular silica-fiber-based distributed temperature sensing systems usually only operate at temperatures below about 800 °C. In this paper, we present the design, implementation, and testing of a distributed ultra-high temperature sensing system using Raman scattering intensity, which operates from room temperature to above 1400 °C. Consideration is given to the impacts of thermal radiation, fluorescence, and the multimode nature of unclad single-crystal fiber to optimize the system. Results from picosecond and sub-nanosecond lasers were compared. Measurements were taken with a ~2 m sapphire optical fiber, which represents the longest commercially available length. Here, a spatial resolution of 12.4 cm and position standard deviation of 0.28 mm were achieved up to the maximum testing temperature of 1400 °C, which is a new record for distributed temperature sensing systems.
Cosmic Bell Test Using Random Measurement Settings from High-Redshift Quasars
Not Available