A model-based DC fault location scheme for multi-terminal MMC-HVDC systems using a simplified transmission line representation

Accurately determining the location of DC pole-to-pole short-circuit faults in modular multilevel converter (MMC) based multi-terminal HVDC (MTDC) systems is key issue in ensuring fast power recovery. This paper proposes an effective DC fault location scheme for the MMC-MTDC that uses an estimated R-L representation of the transmission lines. By using the measured voltage and current data from both ends of the faulted DC line, the proposed fault location formulas can calculate the location of the fault with high accuracy. The simplified R-L representation greatly reduces the computation burden of the fault detection algorithm. Electromagnetic transient (EMT) simulations of a four-terminal MMC-MTDC system on PSCAD/EMTDC are used to confirm the effectiveness of the proposed approach. The results verify that the proposed scheme is robust and almost not affected by the transmitted power or the fault resistance

The First Example of Tb-3-Containing Metallopolymer-Type Hybrid Materials with Efficient and High Color-Purity Green Luminescence

In the series of homo-leptic trinuclear complexes {[Ln(3)(L)(4)Cl-4(MeOH)(H2O)]center dot Cl} (Ln = La, 1; Ln = Eu, 2; Ln = Tb, 3 or Ln = Gd, 4) self-assembled from the allyl-modified benzimidazole-type ligand HL (4-allyl-2-(1H-benzo[d]imidazol-2-yl)-6-methoxyphenol) and LnCl(3)center dot 6H(2)O, a suitable energy level match endows efficient green luminescence (Phi(overall) = 72%) of Tb-3-arrayed complex 3. The copolymerization between each of these complex monomers 1-4 and C=C-containing MMA (methyl methacrylate) or NBE (norbornene) shows that degradative chain transfer of the terminal four flexible allyl groups within restrains their radical polymerization with MMA while it does not hinder their effective ring-opening metathesis polymerization (ROMP) with NBE. Thus, two kinds of PMMA-supported doping hybrid materials 1@PMMA, 2@PMMA, 3@PMMA and 4@PMMA and PNBE-supported metallopolymer-type hybrid materials Poly( NBE-1), Poly(NBE-2), Poly(NBE-3) and Poly(NBE-4) are obtained, respectively. Especially for both 3@PMMA and Poly(NBE-3) with high color-purity characteristic green emission of Tb3+ ions, improved physical properties including significantly enhanced luminescence (Phi(overall) = 76% or 83%) are observed, and covalent-bonding endows a higher-concentration self-quenching as compared to physical doping.National Natural Science Foundation 21373160, 91222201, 21173165Program for New Century Excellent Talents in University from the Ministry of Education of China NCET-10-0936Doctoral Program of Higher Education 20116101110003Science and Technology and Innovation Project of Shaanxi Province 2012KTCQ01-37Graduate Innovation and Creativity Fund (Visiting Learner) of Northwest University in P. R. ChinaChemistr

A multi-port current-limiting hybrid DC crcuit breaker

Recently the hybrid multi-port DC circuit breaker (MP-DCCB) is becoming popular in protecting HVDC grids, thanks to their re-duction of power electronics devices. In this paper, an enhanced multi-port current-limiting DCCB (MP-CLCB) for multiple line protection is proposed. The integrated fault current limiter (FCL) inside the MP-CLCB can clear the fault faster with slightly in-creased costs. To reduce the energy dissipation requirement for the surge arresters caused by the newly added current-limiting path, an energy transfer path which provides a loop with the in-ductors during the current decay stage is designed. The theoreti-cal analysis of the pre-charging, current-limiting, fault interrup-tion and energy dissipation of the MP-CLCB is carried out. Moreover, the design principles of the energy dissipation and the key parameters of the MP-CLCB are provided. The proposed approaches are verified through simulations in PSCAD/EMTDC. The results show that the MP-CLCB can replace multiple DCCBs, accelerate the fault current interruption and reduce the energy dissipation requirement for the surge arresters

Three-dimensional Pentagon Carbon with a genesis of emergent fermions

Carbon, the basic building block of our universe, enjoys a vast number of allotropic structures. Owing to its bonding characteristic, most carbon allotropes possess the motif of hexagonal rings. Here, with first-principles calculations, we discover a new metastable three-dimensional carbon allotrope entirely composed of pentagon rings. The unique structure of this "Pentagon Carbon" leads to extraordinary electronic properties, making it a cornucopia of emergent topological fermions. Under lattice strain, Pentagon Carbon exhibits topological phase transitions, generating a series of novel quasiparticles, from isospin-1 triplet fermions, to triply-degenerate fermions, and further to concatenated Weyl-loop fermions. Its Landau level spectrum also exhibits distinct features, including a huge number of almost degenerate chiral Landau bands, implying pronounced magneto-transport signals. Our work not only discovers a remarkable carbon allotrope with highly rare structural motifs, it also reveals a fascinating hierarchical particle genesis with novel topological fermions beyond the Dirac and Weyl paradigm

Near-net forming complex shaped Zr-based bulk metallic glasses by high pressure die casting

Forming complex geometries using the casting process is a big challenge for bulk metallic glasses (BMGs), because of a lack of time of the window for shaping under the required high cooling rate. In this work, we open an approach named the “entire process vacuum high pressure die casting” (EPV-HPDC), which delivers the ability to fill die with molten metal in milliseconds, and create solidification under high pressure. Based on this process, various Zr-based BMGs were prepared by using industrial grade raw material. The results indicate that the EPV-HPDC process is feasible to produce a glassy structure for most Zr-based BMGs, with a size of 3 mm × 10 mm and with a high strength. In addition, it has been found that EPV-HPDC process allows complex industrial BMG parts, some of which are hard to be formed by any other metal processes, to be net shaped precisely. The BMG components prepared by the EVP-HPDC process possess the advantages of dimensional accuracy, efficiency, and cost compared with the ones formed by other methods. The EVP-HPDC process paves the way for the large-scale application of BMGs

BacHBerry: BACterial Hosts for production of Bioactive phenolics from bERRY fruits

BACterial Hosts for production of Bioactive phenolics from bERRY fruits (BacHBerry) was a 3-year project funded by the Seventh Framework Programme (FP7) of the European Union that ran between November 2013 and October 2016. The overall aim of the project was to establish a sustainable and economically-feasible strategy for the production of novel high-value phenolic compounds isolated from berry fruits using bacterial platforms. The project aimed at covering all stages of the discovery and pre-commercialization process, including berry collection, screening and characterization of their bioactive components, identification and functional characterization of the corresponding biosynthetic pathways, and construction of Gram-positive bacterial cell factories producing phenolic compounds. Further activities included optimization of polyphenol extraction methods from bacterial cultures, scale-up of production by fermentation up to pilot scale, as well as societal and economic analyses of the processes. This review article summarizes some of the key findings obtained throughout the duration of the project