ISRN Power Engineering The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Characteristics of Helium Gas with High Temperature and High Pressure Flowing through a 90-Degree Elbow Mon, 14 Apr 2014 11:14:57 +0000 There exists a certain 90° elbow structures in the helium circulation of HTGR-10. In terms of energy-saving and design simplification of reactor’s primary loop, 90° elbow can be used to measure the helium flow and the content of water vapor, both of which are significant in an accident. It is necessary to make an in-depth research of the flow characteristics of helium flowing 90° elbow. Simulation results indicate that fluid’s motion in the elbow is under the control of the centrifugal forces. Static pressure near the extrados is higher than that near the intrados. Boundary layer separation occurs at the latter half intrados of the elbow. The vortex emerges during the separation process and increases the energy dissipation. Velocity in the near-intrados region is higher than that in the near-extrados region, which is opposite to the pressure distribution trend. Under the action of the centrifugal forces, the secondary flow emerges in the latter half of the elbow and complicates the flow field by generating two vortexes which rotate in a different direction. Beibei Feng, Yanfei Sun, Xingtuan Yang, Shengqiang Li, Jiyuan Tu, and Shengyao Jiang Copyright © 2014 Beibei Feng et al. All rights reserved. Optimal Overcurrent Relay Coordination Using Optimized Objective Function Thu, 03 Apr 2014 14:25:27 +0000 A novel strategy for directional overcurrent relays (DOCRs) coordination is proposed. In the proposed method, the objective function is improved during the optimization process and objective function coefficients are changed in optimization problem. The proposed objective function is more flexible than the old objective functions because various coefficients of objective function are set by optimization algorithm. The optimization problem is solved using hybrid genetic algorithm and particle swarm optimization algorithm (HGAPSOA). This method is applied to 6-bus and 30-bus sample networks. Seyed Hadi Mousavi Motlagh and Kazem Mazlumi Copyright © 2014 Seyed Hadi Mousavi Motlagh and Kazem Mazlumi. All rights reserved. Novel Technologies for Design and Analysis of Switching Mode Power-Supply Circuit Based on Solitary Electromagnetic Wave Theory Tue, 04 Mar 2014 08:50:12 +0000 The novel solitary electromagnetic wave (SEMW) theory and the novel design methodologies of the switching mode power supply circuit (SMPC) are presented. The SEMW theory was developed as a basic theory of the design of all kinds of the switching mode circuit including SMPC by fusing the physics of semiconductor, nonlinear undulation, and electromagnetic wave. When the SEMW theory is used, the electromagnetic analysis of SMPC becomes possible by using only the real parameters based on the physics. The technologies of the low impedance lossy line (LILL) which is used to the DC line and the matched impedance lossy line (MILL) which is used to the switching line are also presented. They are effective for suppressing the electromagnetic interference. SMPC can be reconfigured to the quasistationary state closed circuit (QSCC) by applying LILL and MILL in accordance with the SEMW theory. No electromagnetic interference exist in QSCC. The buck converter which is one of the most popular DC-DC converters is presented as an example of the method for being reconfigured to QSCC. The conventional design tools which includes SPICE based on the AC circuit theory will be effective for the design and analysis of the inside circuit of QSCC. Hirokazu Tohya and Noritaka Toya Copyright © 2014 Hirokazu Tohya and Noritaka Toya. All rights reserved. Solution to Security Constrained Environmental Pumped-Storage Hydraulic Unit Scheduling Problem by Genetic Algorithm Sun, 22 Sep 2013 15:07:51 +0000 A lossy electric power system area that contains thermal units and a pumped-storage (p-s) hydraulic unit is considered in this paper. The cost function, which is weighted combination of the total fuel cost and the total emission cost of the thermal units, in an operation cycle, is minimized under some possible electric and hydraulic constraints. The dispatch technique that is based on genetic algorithm considers minimum and maximum reservoir storage limits of the p-s unit, upper and lower active and reactive generation limits of the thermal units, upper and lower active pumping/generation power limits of the p-s unit, maximum transmission capacities of the transmission lines, and upper and lower limits of the bus voltage magnitudes in a considered power system. The proposed dispatch technique was tested on an example power system that has 12 buses with five thermal units and a p-s hydraulic unit. The same dispatch problem is solved via an iterative solution method based on modified subgradient algorithm operating on feasible values (F-MSG) and pseudowater price just for comparison purpose. It is seen that the solution technique based on the F-MSG algorithm and pseudowater price gives similar results with the proposed algorithm based on genetic algorithm. Salih Fadil, Cüneyt Demir, and Burak Urazel Copyright © 2013 Salih Fadil et al. All rights reserved. Real-Time State Estimation in the Cameroon Power System Mon, 16 Sep 2013 09:47:26 +0000 An important tool for the energy management system (EMS) is state estimation. Based on measurements taken throughout the network, state estimation gives an estimation of the state variables of the power system while checking that these estimates are consistent with the measurements. Currently, in the Cameroon power system, state estimates have been provided by ad hoc supervisory control and data acquisition (SCADA) systems. A disadvantage is that the measurements are not synchronised, which means that state estimation is not very precise during dynamic phenomena in the network. In this paper, real-time phasor measurement units (PMUs) that provide synchronised phasor measurements are proposed for integration into the power system. This approach addresses two important issues associated with the power system state estimation, namely, that of measurement accuracy and that of optimization of the number of measurement sites, their location, and the importance given to their measurements on the dynamic state estimation. Emmanuel Tanyi and Edwin Mbinkar Copyright © 2013 Emmanuel Tanyi and Edwin Mbinkar. All rights reserved. Broadband over Power Lines Systems Convergence: Multiple-Input Multiple-Output Communications Analysis of Overhead and Underground Low-Voltage and Medium-Voltage BPL Networks Sun, 15 Sep 2013 13:33:27 +0000 This review paper reveals the broadband potential of overhead and underground low-voltage (LV) and medium-voltage (MV) broadband over power lines (BPL) networks associated with multiple-input multiple-output (MIMO) technology. The contribution of this review paper is fourfold. First, the unified value decomposition (UVD) modal analysis is introduced. UVD modal analysis is a new technique that unifies eigenvalue decomposition (EVD) and singular value decomposition (SVD) modal analyses achieving the common handling of traditional SISO/BPL and upcoming MIMO/BPL systems. The validity of UVD modal analysis is examined by comparing its simulation results with those of other exact analytical models. Second, based on the proposed UVD modal analysis, the MIMO channels of overhead and underground LV and MV BPL networks (distribution BPL networks) are investigated with regard to their inherent characteristics. Towards that direction, an extended collection of well-validated metrics from the communications literature, such as channel attenuation, average channel gain (ACG), root-mean-square delay spread (RMS-DS), coherence bandwidth (CB), cumulative capacity, capacity complementary cumulative distribution function (CCDF), and capacity gain (GC), is first applied in overhead and underground MIMO/LV and MIMO/MV BPL channels and systems. It is found that the results of the aforementioned metrics portfolio depend drastically on the frequency, the power grid type (either overhead or underground, either LV or MV), the MIMO scheme configuration properties, the MTL configuration, the physical properties of the cables used, the end-to-end distance, and the number, the electrical length, and the terminations of the branches encountered along the end-to-end BPL signal propagation. Third, three interesting findings concerning the statistical properties of MIMO channels of distribution BPL networks are demonstrated, namely, (i) the ACG, RMS-DS, and cumulative capacity lognormal distributions; (ii) the correlation between RMS-DS and ACG; and (iii) the correlation between RMS-DS and CB. By fitting the numerical results, unified regression distributions appropriate for MIMO/BPL channels and systems are proposed. These three fundamental properties can play significant role in the evaluation of recently proposed statistical channel models for various BPL systems. Fourth, the potential of transformation of overhead and underground LV/BPL and MV/BPL distribution grids to an alternative solution to fiber-to-the-building (FTTB) technology is first revealed. By examining the capacity characteristics of various MIMO scheme configurations and by comparing these capacity results against SISO ones, a new promising urban backbone network seems to be born in a smart grid (SG) environment. Athanasios G. Lazaropoulos Copyright © 2013 Athanasios G. Lazaropoulos. All rights reserved. Increase Performance of IPMSM by Combination of Maximum Torque per Ampere and Flux-Weakening Methods Tue, 20 Aug 2013 09:08:58 +0000 Interior permanent magnet motor (IPMSM) was used as air conditioner compressor to reduce the power consumption and improve the performance of the system. Two control methods including maximum torque per ampere (MTPA) and flux-weakening methods were employed to increase the speed range of the air conditioner compressor. The present study adapted the flux weakening algorithm technique which can be used for constant torque and constant power regions. Results indicated that the operation speed range of the IPMSM may increase significantly by using the proposed flux weakening algorithm. Saman Toosi, Mohammad Rezazadeh Mehrjou, Mahdi Karami, and Mohammad Reza Zare Copyright © 2013 Saman Toosi et al. All rights reserved. On the Transient Response and the Frequency Analysis of Transmission Line Towers Thu, 11 Apr 2013 17:40:53 +0000 This paper proposes an approach to the study of the transient response and the frequency characteristics of power lines' towers, when subjected to lightening strikes. It starts with dividing the nonuniform line representing the tower into a number of sections. From the usually known dependence of the tower's characteristic impedance on the vertical coordinate and the application of a recursive circuit reduction technique, an s-domain expression for the tower input impedance can be obtained. This expression, followed by the numerical Laplace inversion, is utilized for the determination of the tower's transient response. The impedance expression can be also used to determine the tower's resonance frequencies. This was used to demonstrate some potentially critical situations in which the tower is hit by lightning strikes comprising multiple current pulses. The validity of the proposed technique is demonstrated by comparing the achieved results with those already available in the literature for the same case studies. Mohamed M. Saied Copyright © 2013 Mohamed M. Saied. All rights reserved.