Copyright (c) 2009 Berkeley Electronic Press All rights reserved. http://www.bepress.com/ijeeps Recent documents in International Journal of Emerging Electric Power Systems en-us Mon, 16 Nov 2009 23:25:03 PST 3600 http://www.bepress.com/ijeeps/vol10/iss5/art3 http://www.bepress.com/ijeeps/vol10/iss5/art3 Sun, 15 Nov 2009 18:32:41 PST Ever growing demand for the electric power requires timely expansion of generations and networks. It is observed that these expansions may not often be done optimally and the load concentration locations and generation expansion locations may not always match up. To address this problem of meeting the growing loads optimally, a concept of relative electrical distance (RED) is applied to identify the optimum generation reschedule values and also system expansion locations. The approach of RED computes the relative electrical distances between the generation and load buses using the transmission network parameters. Using this approach, the amount of generation increase or evacuation required can be identified. This paper presents the approach using a sample 16-bus system and a practical 72-bus system, an equivalent of Indian southern grid. Studies are carried out considering short term and long term load growths and the results obtained are validated using power flows. The different scenarios studied are assessed based on their minimum voltage, MW loss values, Minimum Singular Value etc. Few aspects like cost estimation for network expansion, loss shared by different generations etc, are also computed, and it is finally concluded that the best tradeoff between the two expansions is to be honored. Thukaram Dhadbanjan Power system planning Deregulated power systems Static Voltage stability http://www.bepress.com/ijeeps/vol10/iss5/art2 http://www.bepress.com/ijeeps/vol10/iss5/art2 Sun, 15 Nov 2009 16:40:56 PST This paper presents an approach to model current transformers (CTs) by visual inspection of hysterisis loops. Three parameters on CT hysterisis loops reveal enough information about the core-loss and non-linear magnetizing inductance that power measurements and flux-current data-pairs can be avoided. To validate the proposed model, an experimental CT is saturated with energizations and compared to simulation results. Overlays of the experimental energizations, the proposed modeling approach, and the traditional piecewise-linear approach are compared. Fabian M. Uriarte power systems distribution systems modeling simulation http://www.bepress.com/ijeeps/vol10/iss5/art1 http://www.bepress.com/ijeeps/vol10/iss5/art1 Tue, 27 Oct 2009 07:09:57 PDT In an electricity market, suppliers are more concerned with maximizing their profit and minimizing the financial risk, which can be achieved through strategic bidding. In this paper, Equal Incremental Cost Criteria (EICC) has been used for developing the optimal bidding strategy. The rival's bidding behavior has been formulated using a stochastic optimization model. Genetic Algorithm (GA), along with ac sensitivity factors, has been used to decide the optimal bidding strategy including congestion management to maximize the profit of the suppliers, considering single sided as well as double sided bidding. Both pure as well as probabilistic strategies have been simulated. Results with Sequential Quadratic Programming (SQP), a classical optimization method, and dc sensitivity factors have also been obtained to compare and establish the effectiveness of proposed method. Value at Risk (VaR) has been calculated as a measure of financial risk. Arvind Kumar Jain Power system restructuring http://www.bepress.com/ijeeps/vol10/iss4/art8 http://www.bepress.com/ijeeps/vol10/iss4/art8 Sat, 19 Sep 2009 11:50:00 PDT This paper proposes the application of computational intelligence techniques to assist complex problems concerning lightning in transformers. In order to estimate the currents related to lightning in a transformer, a neural tool is presented. ATP has generated the training vectors. The input variables used in Artificial Neural Networks (ANN) were the wave front time, the wave tail time, the voltage variation rate and the output variable is the maximum current in the secondary of the transformer. These parameters can define the behavior and severity of lightning. Based on these concepts and from the results obtained, it can be verified that the overvoltages at the secondary of transformer are also affected by the discharge waveform in a similar way to the primary side. By using the tool developed, the high voltage process in the distribution transformers can be mapped and estimated with more precision aiding the transformer project process, minimizing empirics and evaluation errors, and contributing to minimize the failure rate of transformers. André Nunes De Souza Power Transformers http://www.bepress.com/ijeeps/vol10/iss4/art7 http://www.bepress.com/ijeeps/vol10/iss4/art7 Sat, 19 Sep 2009 11:49:57 PDT There is an attempt to correlate the public health risk with strong magnetic fields from high voltage multiple transmission lines. The statement is based on the public perception that multiple sources of two and three tower lines can generate more radiated fields as compared to single tower. This paper evaluates the fact and figures on realistic situation cases about radiated field exposures based on measurements and simulation models of two and three transmission lines. The case study sites which consist of several towers of 132kV and 275kV lines were located in Melaka district, Malaysia. Measurement procedures of magnetic fields were conducted based on the IEEE/ANSI 644 standard while the dose exposure reference value was based on the public exposures of the ICNIRP limits. The results obtained from this analysis are then compared with the ICNIRP standard for assessing the significance of dose exposure between actual conditions in TNB systems with optimum simulated models of phase arrangements. Recommendations on the threshold value limits at both ROW for the new and existing transmission lines were also proposed in conjunction with development of TNB ELF-EMF policy guidelines. Nazaruddin Abdul Rahman EMF http://www.bepress.com/ijeeps/vol10/iss4/art6 http://www.bepress.com/ijeeps/vol10/iss4/art6 Sat, 19 Sep 2009 11:49:54 PDT Islanded power system can be formed by unexpected electric equipment failure or initiative breaking off of a main system avoiding a whole collapse. Unbalanced power between generation and load may cause an overspeed of the units and trigger the action of Overspeed Protection Controller (OPC) which is mainly designed for a load rejection condition. The mathematic model was built to simulate the islanded system stability with the effect of OPC. The simulation reproduced the power and frequency oscillation as the accidents. The results show a great impact of OPC on the stability of an islanded system. Modified OPC logic was proposed to avoid the oscillation and increase the stability. Lin Gao Power System Stability http://www.bepress.com/ijeeps/vol10/iss4/art5 http://www.bepress.com/ijeeps/vol10/iss4/art5 Fri, 04 Sep 2009 12:35:34 PDT Wind energy conversion systems have become important in the research of renewable energy sources. This is in no small part due to the rapid advances in the size of wind generators as well as the development of power electronics and their applicability in wind energy extraction. However, wind energy has a drawback of having only 1/800 (gm per cubic cm) density as compared to that of water energy. Wind energy does not remain constant and wind turbine output is proportional to the cube of wind speed, which causes the generated power of the wind turbine generator (WTG) to fluctuate. In this paper, a technique is proposed for output power leveling of a wind generation system. Wind turbine blades have a large inertia compared to the inertia of a generator. The inertia of the rotor behaves like an inductor in an electrical circuit. It helps smooth the wind turbine output power, stores energy during acceleration, and restores energy during deceleration. The effectiveness of output power leveling control is verified by simulations for the wind power generation system. Abdul Motin Howlader Wind Energy http://www.bepress.com/ijeeps/vol10/iss4/art4 http://www.bepress.com/ijeeps/vol10/iss4/art4 Fri, 04 Sep 2009 12:35:32 PDT The analysis of satellite solar power station (SSPS) is carried out for some specified locations in India and consequently the performance of the system is evaluated for geostationary earth orbit (GEO)-based SSPS and low earth orbit (LEO)-based SSPS for sites located at different latitudes. The analysis of power, the received energy over a year, and the received energy during a day for the same beam intensity show better results for LEO-based SSPS system as compared to GEO-based system. However GEO-based system is advantageous in the sense that it will deliver constant energy to the load throughout a year. Thus it is concluded that GEO-based system is suitable for base load power plant. The weight of the rectenna and hence the space required for ground station for same power output for GEO-based system is greater than that for LEO-based system which will in turn increase the overall cost of the GEO-based system. These findings may help for judicious selection of orbit for placing the satellite for SSPS. Kalpana Chaudhary Renewable energy technology http://www.bepress.com/ijeeps/vol10/iss4/art3 http://www.bepress.com/ijeeps/vol10/iss4/art3 Sat, 29 Aug 2009 16:21:06 PDT This paper summarizes international experience of significant clustered photovoltaic systems. Based on the operation experience, major system impacts and corresponding solutions have been studied. Among them, voltage raise of power distribution line due to the reverse power flow from the PV system has been one of the main problems. Therefore, this paper proposes the dynamic and steady-state simulations to evaluate the effectiveness of battery-integrated PV system on avoiding the over voltage problem. Furthermore, different types of battery control modes have been compared. In the simulations, the actual product specifications were adopted as the parameters of the component models, and the largest PV cluster system in Taiwan was chosen as the analyzed demonstration site. The simulation results reveal that the developed control algorithms could avoid voltage rise by setting appropriate control parameter values. In addition, these control algorithms could be applicable to other power grids if appropriate settings are made. Yuan-Kang Wu integration of unconventional sources into existing power systems http://www.bepress.com/ijeeps/vol10/iss4/art2 http://www.bepress.com/ijeeps/vol10/iss4/art2 Sat, 29 Aug 2009 16:21:03 PDT Whether a disturbance will trigger unexpected protection operation to exacerbate the normal operation state or even lead to the unstable state depends on the transient energy that the system gains during the fault period. The paper presents a new gradient projection approach to calculate the critical energy for transient stability assessment of the power system with the protection operation. The method takes the projection of the potential energy gradient on the key protection operation surface as search direction and iteratively searches for the critical energy at the surface; in order to let the optimal point be the feasible point, the generator angles are considered as control variables of power flow equation to solve network bus voltage and angle during the searching process. Examples show that the convergence and precision of the new method proposed is much better than that of other methods, which demonstrates the validity and feasibility of the new method. Jikeng Lin power system stability analysis