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Sun, Wei

Publications and source records attributed to Sun, Wei.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Real-Time Optimized Load Recovery Considering Frequency Constraints

A self-healing power grid can mitigate the impact of power outages and recover the affected area swiftly. To properly size the optimal amount and location of de-energized loads in the presence of both conventional and renewable sources, a precise optimization-based load recovery tool is proposed herein. The steady-state and transient behaviors of loads have been taken into account. The proposed tool contains three separate problems that interact with each other during the restoration period. The first-level problem determines the dispatching of generation units. The second-level problem comprises the non-linear algebraic equations, whose task is to provide the initial conditions for the third-level problem. Finally, the third-level problem intends to determine the optimal location and amount of load pickup through modeling the governor of generators as well as loads' dynamic behaviors. To examine the effectiveness of the proposed tool, a modified IEEE 39-system under a partial blackout condition has been tested. The results are verified by a commercial time-domain simulation software (PSS/E) to demonstrate the accuracy of the proposed approach. Ultimately, the impact of wind turbine frequency control on the load recovery process has been studied under different penetration levels.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2019

Evolution of Solid Electrolyte Interface on TiO 2 Electrodes in an Aqueous Li-Ion Battery Studied Using Scanning Electrochemical Microscopy

Scanning electrochemical microscopy (SECM) was applied for in situ visualization of solid electrolyte interface (SEI) evolution on the TiO 2 anode in a concentrated aqueous electrolyte during cycling. In nonaqueous electrolytes, the SEI is an electronic insulative layer composed of organic and inorganic components covering the electrode surface. However, in concentrated aqueous electrolytes, the SEI is mostly composed of inorganic compounds formed by electrolyte decomposition, such as LiF and Li 2 CO 3 , which are randomly distributed over the TiO 2 surface. In addition, the Ti 3+ and Li residuals accumulated through multiple cycling lead to an increase in the overall electronic conductivity of the TiO 2 anode. Furthermore during the resting period after cycling, an inverse process is observed with partial dissolution of the formed SEI and the diffusion of Li residuals back into the electrolyte.

25 ENERGY STORAGE↗
DOE OSTI2019

A Review of Smart Grid Restoration to Enhance Cyber-Physical System Resilience

The growth in electricity demand and the development of grid modernization have increased the complexity of power grid and driven the grid more vulnerable to extreme events like environmental disasters or man-made attacks. Those disruptions can cause outages, cascading failures, and blackouts. The objectives of this paper are to 1) review the recent development addressing the aforementioned challenges with the focus on the impact of extreme events on power system resilience, and 2) discuss the application of smart grid technologies to provide faster restoration techniques and enhance power system resilience. Moreover, challenges and opportunities for future work to enhance smart grid resilience have also been discussed in this paper. The ultimate goal is to present a summary of state-of-the-art and stimulate interests in the area of cyber-physical- human resilience of smart grid.

Man-made attacks↗
DOE OSTI2019

Distributed Load Restoration in Unbalanced Active Distribution Systems

We present that the resilience of modern power systems has been constantly threatened by various natural disasters and manmade attacks. Under those threats, fast and automatic restoration actions are critical for restoring impacted systems to normal operating conditions and preventing from additional disastrous consequences. Smart grid technologies, such as distributed energy resources (DERs) and microgrids, provide both opportunities and challenges for distribution system restoration. In this paper, distributed load restoration (DLR), in unbalanced active distribution networks is developed using the alternating direction method of multipliers (ADMM) algorithm. The step-by-step restoration actions are provided to schedule the output of DERs and distribution system control devices, as well as the power consumption from transmission system restoration. The nonlinearities from three-phase unbalanced power flow and distribution components modeling are relaxed into a convex quadratic programming model. Then, the problem is decomposed into subproblems for each node by applying ADMM-DLR; and solves through each agent by exchanging limited information with neighboring nodes in an iterative procedure. The developed models and algorithms are validated and demonstrated through testing of the IEEE 13-node and 123-node test feeders. Lastly, simulation results demonstrate the effectiveness of restoring unbalanced distribution system with the hybrid bottom-up and top-down restoration strategies.

14 SOLAR ENERGY↗
DOE OSTI2018

Optimal distribution system restoration using PHEVs

Power outages cost billions of dollars every year and jeopardise the lives of hospital patients. Traditionally, power distribution system takes a long time to recover after a major blackout, due to its top-down operation strategy. New technologies in modern distribution systems bring opportunities and challenges to distribution system restoration. As fast response energy resources, plug-in hybrid electric vehicles (PHEVs) can accelerate the load pickup by compensating the imbalance between available generation and distribution system load. This study provides a bottom-up restoration strategy to use PHEVs for reliable load pickup and faster restoration process. The optimisation problem of finding load pickup sequence to maximise restored energy is formulated as a mixed integer linear programming (MILP) problem. Moreover, the coordination between transmission and distribution restoration is developed to efficiently restore the entire system back to normal operating conditions. Simulation results on one 100-feeder test system demonstrate the efficiency of MILP-based restoration strategy and the benefit from PHEVs to restore more energy in given restoration time. The proposed restoration strategy has great potential to facilitate system operators to achieve efficient system restoration plans. It also provides incentives to deploy a large amount of PHEVs to improve system resiliency.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2018

Optimal self-healing strategy for microgrid islanding

Renewable resource based microgrids provide reliable and cost-effective electricity with low carbon emissions. The flexibility of operating in grid-connected or islanded modes enables a microgrid to serve loads reliably. In the case of unexpected events happening to the main grid, the microgrid will isolate itself and operate in islanded mode to prevent any adversary impacts. The availability of renewable generation in the microgrid has significant impacts on the islanding strategy and different scenarios need to be considered. This study proposes a comprehensive microgrid self-healing strategy under different circumstances. The proposed strategy encompasses generation re-dispatch, network reconfiguration, and load shedding. The microgrid self-healing problem is formulated as a mixed-integer quadratic programming problem, which provides a globally optimal solution to facilitate smooth islanding of the microgrid. A modified Consortium for Electric Reliability Technology Solutions microgrid is used to conduct simulation under various scenarios. The simulation results demonstrate the efficiency of the proposed self-healing strategy in minimising costs of load shedding and generation with optimal switching actions.

optimal self-healing strategy↗
DOE OSTI2018

Interface characteristics of Ti6Al4V-TiAl metal-intermetallic laminate (MIL) composites prepared by a novel hot-pack rolling

Highlights: • The Ti6Al4V/high Nb-TiAl metal-intermetallic (MIL) composite was fabricated. • The formation of γ and α{sub 2} phase at interface is diffusion controlled. • The formation of O phase at interface is due to the segregation of Nb atoms. • The Vickers hardness from Ti6Al4V to TiAl alloy shows a trend of a decrease then an increase and finally a decrease. - Abstract: Ti6Al4V (wt%)/Ti-44Al-8Nb-0.2W-0.2B-0.03Y (at.%) (high Nb-TiAl) metal–intermetallic laminate (MIL) composite with a defect-free interface was successfully prepared by hot-pack rolling and the interface microstructure was characterized by XRD, SEM, EBSD, and TEM techniques. The results showed that the interface was about 260 μm thick and consisted of four different microstructure regions. The thickness of each region was about 60–80 μm and the microstructure of the four regions consisted of acicular O, α{sub 2}, and β/B2 phases; acicular α{sub 2} phase; acicular α{sub 2} and β/B2 phases; and acicular γ, α{sub 2}, and β/B2 phases respectively. The resulting microstructure of the interface region was attributed to the interdiffusion of Ti atoms from the starting Ti6Al4V alloy layer to the high Nb-TiAl alloy layer and Al and Nb atoms from the high Nb-TiAl alloy layer to the Ti6Al4V alloy layer. The formation of acicular α{sub 2} and γ phases was diffusion-controlled and the Nb segregation at the interface caused the formation of O phase which had specific relationships with α{sub 2} and β/B2 phases. The detailed interface microstructural evolution of the Ti6Al4V/high Nb-TiAl MIL composite and the Vickers hardness of the composite are also discussed in this paper.

36 MATERIALS SCIENCE↗
DOE OSTI2018

TPC2 mediates autophagy progression and extracellular vesicle secretion in cancer cells

Autophagy is an evolutionarily conserved lysosomal degradation process, and is involved in various cellular processes. Here we studied the role of two pore channel 2 (TPC2), a lysosomal non-selective Na{sup +}/Ca{sup 2+} channel, in autophagy progression. We found that TPC overexpression in 4T1 mouse breast cancer cell line or in HeLa human cervical cancer cell line inhibited the fusion between autophagosome and lysosome, resulting in the accumulation of autophagosomes accompanied with increased lysosomal pH and TFEB nuclear localization. Interestingly, we also found that extracellular vesicle (EV) secretion was markedly decreased in TPC2 overexpressing cells but was induced in TPC2 knockdown cells. In addition, migration of TPC2 knockdown cells, not TPC2 overexpressing cells, was inhibited. Taken together, these results support a role of TPC2 in autophagy progression and EV trafficking in cancer cells.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Water-Activated VOPO 4 for Magnesium Ion Batteries

Rechargeable Mg batteries, using high capacity and dendrite-free Mg metal anodes, are promising energy storage devices for large scale smart grid due to low cost and high safety. However, the performance of Mg batteries is still plagued by the slow reaction kinetics of their cathode materials. Recent discoveries demonstrate that water in cathode can significantly enhance the Mg-ion diffusion in cathode by an unknown mechanism. Here, we propose the water-activated layered-structure VOPO 4 as a novel cathode material and examine the impact of water in electrode or organic electrolyte on the thermodynamics and kinetics of Mg-ion intercalation/deintercalation in cathodes. Electrochemical measurements verify that water in both VOPO 4 lattice and organic electrolyte can largely activate VOPO 4 cathode. Thermodynamic analysis demonstrates that the water in the electrolyte will equilibrate with the structural water in VOPO 4 lattice, and the water activity in the electrolyte alerts the mechanism and kinetics for electrochemical Mg-ion intercalation in VOPO 4 . Theoretical calculations and experimental results demonstrate that water reduces both the solid-state diffusion barrier in the VOPO 4 electrode and the desolvation penalty at the interface. To achieve fast reaction kinetics, the water activity in the electrolyte should be larger than 10 –2 . The proposed activation mechanism provides guidance for screening and designing novel chemistry for high performance multivalent-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2018

How Water Accelerates Bivalent Ion Diffusion at the Electrolyte/Electrode Interface

The effect of H 2 O in electrolytes and in electrode lattices on the thermodynamics and kinetics of reversible multivalent-ion intercalation chemistry based on a model platform of layered VOPO 4 has been investigated. The presence of H 2 O at the electrolyte/electrode interface plays a key role in assisting Zn 2+ diffusion from electrolyte to the surface, while H 2 O in the lattice structure alters the working potential. More importantly, a dynamic equilibrium between bulk electrode and electrolyte is eventually reached for H 2 O transport during the charge/discharge cycles, with the water activity serving as the key parameter determining the direction of water movement and the cycling stability.

25 ENERGY STORAGE↗
DOE OSTI2018

Integrated Transmission and Distribution Systems Restoration with Distributed Generation Scheduling

The self-healing smart grids enable system operators to quickly and efficiently recover transmission and distribution systems from outages and blackouts. The current restoration procedure solves the transmission and distribution system restoration problems separately without considering their impacts on each other, which may prolong the restoration process. However, with the emerging active distribution networks, distributed generators can contribute into the bottom-up restoration strategy. The interaction between the restoration of two interconnected systems should be taken into account. In this paper, a hybrid model of transmission and distribution systems restoration (HTDSR) is proposed by exchanging data of power and voltage between two separate optimization problems. The effectiveness of the HTDSR algorithm is demonstrated through case studies of the integrated IEEE 13-bus distribution network and IEEE 39-bus transmission grid. Simulation results demonstrate that the integrated restoration strategy with optimal scheduling of distributed generation sources can expedite the restoration process.

Distributed generation↗
DOE OSTI2018

Ambient Electrosynthesis of Ammonia: Electrode Porosity and Composition Engineering

Ammonia, a key precursor for fertilizer production, convenient hydrogen carrier, and emerging clean fuel, plays a pivotal role in sustaining life on Earth. Currently, the main route for NH 3 synthesis is by the heterogeneous catalytic Haber–Bosch process (N 2 +3 H 2 →2 NH 3 ), which proceeds under extreme conditions of temperature and pressure with a very large carbon footprint. Herein we report that a pristine nitrogen–doped nanoporous graphitic carbon membrane (NCM) can electrochemically convert N 2 into NH 3 in an acidic aqueous solution under ambient conditions. The Faradaic efficiency and rate of production of NH 3 on the NCM electrode reach 5.2 % and 0.08 g m –2 h –1 , respectively. Functionalization of the NCM with Au nanoparticles dramatically enhances these performance metrics to 22 % and 0.36 gm –2 h –1 , respectively. In conclusion, as this system offers the potential to be scaled to industrial levels it is highly likely that it might displace the century-old Haber–Bosch process.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of the Ce Content on the Magnetic Properties and Microstructure of CeCo{sub 5}-based Sintered Bulk Magnets

CeCo{sub 5}-based magnets have recently attracted much attention due to their moderate magnetic performance and low cost. Nevertheless, there have been few studies on the effects of Ce content on the magnetic properties and microstructures of CeCo{sub 5}-based magnets. In response to this, the magnetic properties of sintered bulk magnets with nominal compositions of Ce(Co{sub 0.73}Cu{sub 0.135}Fe{sub 0.135}){sub z} (z = 4.95, 5.15, 5.35, and 5.55), prepared by the conventional powder metallurgy method, were investigated here. Based on experimental findings, it was shown that Ce(Co{sub 0.73}Cu{sub 0.135}Fe{sub 0.135}){sub 5.15} sintered bulk magnets had comprehensive magnetic properties—maximum energy product of 80 kJ m{sup − 3} (10 MGOe) and intrinsic coercivity (H{sub cj}) of 452 kA m{sup − 1} (5.69 kOe)—superior to those previously reported by us. For z = 5.35 and 5.55, due to the presence of the minor Ce{sub 2}Co{sub 17} phase (which has a Curie temperature (T{sub c}) < 20 °C), magnets had low H{sub cj} values. Based on x-ray diffraction and scanning electron microscopy observations, it was suggested that the volume fraction of the 1:5 matrix phase was the main factor determining the H{sub cj} of CeCo{sub 5}-based sintered bulk magnets obtained with different Ce contents. Furthermore, the importance of the dispersion characteristics of the Ce{sub 2}O{sub 3} phase within the matrix was emphasized. Uniform dispersion of the Ce{sub 2}O{sub 3} phase can significantly improve the overall magnetic performance of CeCo{sub 5}-based magnets.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Chance-constrained Service Restoration for Distribution Networks with Renewables

Power systems operation is facing great challenges from natural disasters and cyber-attacks. It is critical but also difficult to enhance the reliability and resilience against extreme events. To better response to inevitable outages or blackouts, service restoration in distribution networks is important to minimize the disastrous impacts of catastrophic events. The increasing penetration of distributed energy resources (DERs) provides new opportunities to expedite the restoration process. However, the coordination with conventional distribution system control devices and the uncertainty and variability of intermittent renewable energy resources requires new operation and control strategies for distribution service restoration (DSR). This paper develops an optimal bottom-up DSR strategy by coordinating DERs with voltage regulators and capacitor banks. The chance-constrained (CC) programming approach is used to model the probabilistic output limit of solar radiation and PV generation. The Markov's inequality and Latin hypercube sampling techniques are applied to convert and incorporate the chance constraints into the DSR optimization problem. The CC-DSR problem is formulated as a mixed integer convex programming problem, considering various operational cost functions and bidirectional three-phase unbalanced load flow. Simulation results on the modified IEEE 13-node test feeder system demonstrate the effectiveness and flexibility of the bottom-up DSR strategy.

Chance constrained optimization, Distribution serv↗