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1

Optimal scheduling of Virtual Power Plant with risk management

Xia Y., Liu J.

Journal of Power Technologies

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2016

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Vol. 96, nr 1

49--56

EN

Due to intense electricity consumption, environmental concerns and technological development, a great number of renewable distributed resources have been widely installed in the distributed network. However, the reality that renewable distributed resources frequently fluctuate under high penetration makes effective use a challenge. Fortunately, with improved communication architecture and control techniques, this could be achieved by a Virtual Power Plant (VPP). VPP can aggregate various resources in a distributed generation portfolio, by creating one single operating profile. The aim of this paper is mainly to analyze optimal scheduling of VPP to maximize its profit, with due consideration given to the uncertainty of renewable energy output, such as wind power, and to make the energy mix respond to system need. A risk quantization method (CVaR) is introduced to deal with uncertainty. This paper presents a VPP scheduling model, which takes VPP total operation cost, traded electricity cost, unit earnings, supply-demand balancing and other constraints into account, with a CVaR assessment method embedded into this model. According to the scenarios generated by uncertainty of wind power output, numerical results for a proposed case are discussed. These results show the expected profit of VPP scheduling is closely associated with different degrees of confidence , which is a great help for VPP operators when making the tradeoff between risk and profit.

2

Internal Friction of Li7La3Zr2O12 Based Lithium Ionic Conductors

Wang X. P., Song L., Hu J., Xia Y. P., Xia Y., Gao Y. X., Zhang L. C., Magalas L. B., Fang Q. F.

Archives of Metallurgy and Materials

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2016

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Vol. 61, iss. 1

21--24

EN

The diffusion mechanisms of lithium ions in tetragonal phase as well as in Al and Nb stabilized cubic Li7La3Zr2O12 compounds were investigated by low-frequency internal friction technique. In the cubic Li7La3Zr2O12 phase, a remarkable relaxation-type internal friction peak PC with a peak height up to 0.12 was observed in the temperature range from 15°C to 60°C. In the tetragonal phase however, the height of the PT peak dropped to 0.01. The obvious difference of the relaxation strength between the cubic and tetragonal phases is due to the different distribution of lithium ions in lattice, ordered in the tetragonal phase and disordered in the cubic phase. Based on the crystalline structure of the cubic garnet-type Li7La3Zr2O12 compound, it is suggested that the high internal friction peak in the cubic phase may be attributed to two diffusion processes of lithium ions: 96h↔96h and 96h↔24d.

3

A Generic Methodological Framework for Cyber-ITS : Using Cyber-infrastructure in ITS Data Analysis Cases

Xia Y., Zhang T., Wang S.

Fundamenta Informaticae

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2014

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Vol. 133, nr 1

35--53

EN

This paper presents a method to capture the computational intensity and computing resource requirements of data analysis in intelligent transportation systems (ITS). These requirements can be transformed into a generic methodological framework for Cyber-ITS, mainly consisting of region-based ITS data divisions and tasks scheduling for processing, to support the efficient use of cyber-infrastructure (CI). To characterize the computational intensity of a particular ITS data analysis, the computational transformation is performed by data-centric and operation-centric transformation functions. The application of this framework is illustrated by two ITS data analysis cases: multi-sensor data fusion for traffic state estimation by integrating rough set theory with Dempster- Shafer (D-S) evidence theory, and geospatial computation on Global Positioning System (GPS) data for advertising value evaluation. To make the design of generic parallel computing solutions feasible for ITS data analysis in these cases, an approach is developed to decouple the region-based division from specific high performance computer (HPC) architecture and implement a prototype of the methodological framework. Experimental results show that the prototype implementation of the framework can be applied to divide the ITS data analysis into a load-balanced set of computing tasks, therefore facilitating the parallelized data fusion and geospatial computation to achieve remarkable speedup in computation time and throughput, without loss in accuracy.

4

Structure Design and Performance Analysis of Substation Area Backup Protection Communication Network in Smart Substation

Chen L., Zhang K., Xia Y., Hu G.

Przegląd Elektrotechniczny

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2013

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R. 89, nr 5

182-186

EN

In this paper, the general design of substation area backup protection (SABP) communication network in smart substation is proposed, and taking a practical 220kV smart substation for the application object, the communication network’s specific structure is constructed. Besides, the specific network’s real-time performance is studied based on theoretical analysis and OPNET simulation, and its reliability is calculated according to reliability block diagram and fault tree combining with Bayesian technology. The results show that the two performances can meet the requirements.

PL

W artykule przedstawiono projekt sieci komunikacyjnej na potrzeby rezerwowego systemu zabezpieczeń w obszarze inteligentnej podstacji elektroenergetycznej. Proponowaną strukturę sieci zaimplementowano dla inteligentnej podstacji 220kV. Przeprowadzono także symulacje (OPNET) i analizę teoretyczną wydajności sieci w czasie rzeczywistym oraz parametrycznie określono jej niezawodność.

5

A Method to Estimate Leakage Current of Polluted Insulators

Xia Y., Jiang X., Sun C., Dong B.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 3b

161-164

EN

The effects of the applied voltage(U), equivalent salt deposit density (�PESDD) and relative humidity density(RH) on the leakage current (LC) are studied based on the least squares algorithm (LSA) in this study. Experiments' results show that, the maximal amplitude of LC Ih increases with the increase of �PESDD by an power function with a positive index 0.451, while increases with the increase of both U and RH by an exponential function with a positive index 0.017 for U and 9.751 for RH. The result can be used to evaluate the pollution condition of insulators based on LC.

PL

Zbadano prąd upływu zabrudzonych izolatorów uwzględniając przyłożone napięcie, względne zasolenia i względna wilgotność. Stwierdzono, że prąd upływu rośnie wraz z zasoleniem ze współczynnikiem potęgowym 0.45.

6

Investigation on Irreversible Expansion of 1,3,5-Triamino-2,4,6-trinitrobenzene Cylinder

Sun J., Kang B., Zhang H., Liu Y., Xia Y., Yao Y., Liu X.

Central European Journal of Energetic Materials

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2011

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Vol. 8, nr 1

69-79

EN

In this study, the irreversible expansion of TATB cylinder is investigated. No evident variation of the lattice parameters is observed on TATB crystal. The density of TATB powder decreases by only about 0.02% after it suffered from thermal cycling process at the range from -54 C to 74 C, while the density of TATB cylinder decreases by about 1.0%. It is suggested that the density variation of TATB powder has little contribution to the density decrease of TATB cylinder. Therefore, the increasing interstices between TATB powder originated from the thermal cycling should be responsible to the irreversible expansion of TATB cylinder.

7

Effects of Short-chain Alcohols on the Phase Behavior, Solubilities and Solubilization Ability in Microemulsion Systems

Xia Y., Li H. L., Chai J. L., Yu X. Y., Liu J., Qin C. K., Chen J. F.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 2

315-324

EN

The effects of short-chain alcohols on the phase behavior, solubilities and solubilization ability in the microemulsion systems cetyltrimethyl ammonium bromide (CTAB) or cetylpyridinium bromide (CPB) or 1-hexadecyl-3-methylimidazolium bromide (C16mimBr)/1-propanol or 1-butanol or 1-pentanol/n-octane/brine were investigated with the d-g fishlike phase diagram. The phase diagram was affected greatly by alcohols, and the magnitude of the middle phase region in the fish body is in the order 1-propanol greated than greated than 1-butanol greated than1-pentanol. With the carbon chain length becoming shorter, more alcohol molecules are needed to balance the interfacial layer. Nearly all surfactants enter into the interfacial layer and little remains in aqueous or oleic phase. However, alcohols dissolve in the aqueous and oleic phases, besides they enter into the interfacial layer. The solubilization ability of the microemulsion system is mainly affected by the alcohols and the order is 1-pentanol greated than 1-butanol greated than 1-propanol.

8

Lqr-Based Nonlinear Tuning Relay Control Design With Fast Convergence

Yu X., Xia Y., Ledwich G., Oghanna W.

International Journal of Applied Mathematics and Computer Science

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1999

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Vol. 9, no 2

313-326

EN

In this article, we present a relay control scheme based on LQR design with fast convergence. This scheme provides a practical and simple way to achieve fast convergence based on the well-known LQR design principle. The controller is a global stabiliser in the sense that for any given initial condition, we can always initialize the controller to drive the system to reach the origin. This controller is tunable in accordance with the position of the system state: the closer to the origin, the larger the control gains, which results in a fast control that maintains bounded control magnitude. It has also been shown that setting matrix Q can significantly influence the tendency of eigenvalues to switch the hyperplane. The relation between matrix Q and the tendency of those eigenvalues has been identified. Simulation results are presented to demonstrate the effectiveness of the scheme.