06 Electrical power supply and utilization (scientific, technical)

network. Case studies on IEEE 14-bus test system, IEEE 24-bus reliability test system, IEEE 30-bus test system and IEEE 57-bus test system are presented. The results represent the variation of critical switching time against parameters of aggregate load and system conditions.

05•02081 Design and experimental tests of control strategies for active hybrid fuel cell/battery power sources Jiang, Z. et al. Journal of Power Sources, 2004, 130, (1 2), 163 171. Twenty-first century handheld electronic devices and new generations of electric vehicles or electric airplanes have fuelled a need for new high-energy, high-power, small-volume, and lightweight power sources. Current battery technology by itself is insufficient to provide the mandatory long-term power these systems require. Fuel cells are also unable to provide the essentially high-peak power demanded by these systems. Hybrid systems composed of fuel cells and secondary batteries could combine the high power density of clean fuel cells and the high energy density of convenient batteries. This paper presents an experimental study on control strategies for active power sharing in such a hybrid fuel cell/battery power source. These control strategies limited the fuel cell current to safe values while also regulating the charging current or voltage of the battery. The several tested control strategies were implemented in MATLAB/Simulink and then tested under the pulsed-current load condition through experiments. Exper- imental tests were conducted with three control objectives: maximum fuel cell power, maximum fuel cell efficiency, and adaptive.

05•02082 Electric power generation by super-adiabatic combustion in thermoelectric porous element Hanamura, K. et al. Energy, 2005, 30, (2 4), 347 357. A new system for converting combustion heat into electric power was proposed on the basis of reciprocating-flow super-adiabatic combus- tion in a catalytic and thermoelectric porous element. Self-sustaining combustion of an extremely low-calorific gas was successfully achieved in the element; because a reciprocating flow in the porous element recirculated energy, effectively regenerating combustion gas enthalpy into an enthalpy increase in the low-calorific gas. In the combustion system, a trapezoidal temperature distribution was established along the flow direction, resulting in a steep temperature gradient in the thermoelectric porous element. Numerical simulation showed that 94% of the combustion heat was transferred through the thermoelectric element by conduction. As a result, the total thermal efficiency, which was defined as the ratio of the electric power generated to the combustion heat, attained a value close to the conversion efficiency of the thermoelectric device itself.

05•02083 Evolutionary programming based security constrained optimal power flow Somasundaram, P. et al. Electric Power Systems Research, 2004, 72, (2), 137 145. This paper presents an algorithm for solving security constrained optimal power flow problem through the application of evolutionary programming (EP). The controllable system quantities in the base-case state are optimized to minimize some defined objective function subject to the base-case operating constraints as well as the contingency-case security constraints. An IEEE 30-bus system is taken for investigation. The security constrained optimal power flow results obtained using EP are compared with those obtained using conven- tional security constrained optimal power flow. The investigations reveal that the proposed algorithm is relatively simple, reliable and efficient and suitable for on-line applications.

05•02084 Experimental study of advanced cogeneration system with ammonia-water mixture cycles at bottoming Takeshita, K. et al. Energy, 2005, 30, (2 4), 247 260. In this study, an advanced cogeneration system (ACGS) composed of three turbine systems and an ammonia absorption refrigerator is presented. The overall system configurations and some experimental results of the steady state are shown. The effectiveness of the bottoming stage that employs an ammonia water mixture (AWM) as the working fluid is confirmed by experimental investigation. The experimental investigation shows that the AWM bottoming power- refrigeration cycles contributes to a higher bottoming efficiency, which is about 7.0% in electric power. Otherwise, the efficiency at the middle stage in conventional combined gas and steam turbine power plants is 4.6%. The cogeneration efficiency at the bottoming reached about 26.5%, which is the heat and power ratio to the heat input from the heat recovery steam generator.

05•02085 Ferritic stainless steels as bipolar plate material for polymer electrolyte membrane fuel cells Wang, H. and Turner, J. A. Journal of Power Sources, 2004, 128, (2), 193 200.

308 Fuel and Energy Abstracts September 2005

Both interracial contact resistance (ICR) measurements and electro- chemical corrosion techniques were applied to ferritic stainless steels in a solution simulating the environment of a bipolar plate in a polymer electrolyte membrane fuel cell (PEMFC). Stainless steel samples of AISI434, AISI436, AISI441, AISI444, and AISI446 were studied, and the results suggest that AISI446 could be considered as a candidate bipolar plate material. In both polymer electrolyte membrane fuel cell anode and cathode environments, AISI446 steel underwent passivation and the passive films were very stable. An increase in the ICR between the steel and the carbon backing material due to the passive film formation was noted. The thickness of the passive film on AISI446 was estimated to be 2.6 nm for the film formed at 0.1 V in the simulated PEMFC anode environment and 3.0 nm for the film formed at 0.6 V in the simulated PEMFC cathode environment. Further improvement in the ICR will require some modification of the passive film, which is dominated by chromium oxide.

05•02086 Frequency domain transient analysis of electrical networks including non-linear conditions Moreno, P. et al. hTternational Journal o f Electrical Power & Energy Systems, 2005, 27, (2), 139 146. This paper describes a method for the analysis of electromagnetic transients in multiphase transmission networks using the Numerical Laplace Transform. The proposed procedure is based on the super- position principle and is applied to switching and non-linear elements modelling. Switching operations are modelled as initial condition problems by means of injected current sources. In the case of non- linear elements, a piece-wise linear approximation is made, which reduces the problem to a sequence of switching operations. Several applications and comparisons with results obtained with the EMTDC and ATP programs are presented.

05•02087 Hardware implementation of a fuzzy logic stabilizer on a laboratory scale power system Al-Osaimi, S/A. eta[. Electric Power Systems Research, 2005, 74, (1), 9 15. A power system stabilizer using the fuzzy logic is designed and implemented in this paper. Simulation studies are performed to evaluate the performance of the fuzzy logic power system stabilizer (FLPSS) and PID power system stabilizer (PIDPSS). Genetic algorithms have been used to optimize the parameters of the fuzzy and PID stabilizers. To validate the design, different types of disturbances are applied to the system and the results of both stabilizers are compared. The simulation studies show that the fuzzy stabilizer provides a relatively better performance comparable to that of the PIDPSS over a wide range of operating conditions. The FLPSS and PIDPSS have also been experimentally implemented using MATLAB/Real-Time Windows Target toolbox software on a labora- tory set up to model a simple power system of 1 KVA machine connected to an infinite bus through a transmission line. Experimental tests and results revealed the effectiveness of FLPSS, especially in vulnerable operating points.

05•02088 Improving electric load forecasts using network committees Abdel-Aal, R. E. et a[. Electric Power Systems Research, 2005, 74, (1), 83 94. Accurate daily peak load forecasts are important for secure and profitable operation of modern power utilities, with deregulation and competition demanding ever-increasing accuracies. Machine learning techniques including neural and abductive networks have been used for this purpose. Network committees have been proposed for improving regression and classification accuracy in many disciplines, but are yet to be widely applied to load forecasting. This paper presents a formal approach to apply the technique using historical load and temperature data spanning multiple years, with individual committee members trained on different years. Correlation among data for successive years is investigated and methods to enhance independence between member models for improving committee performance are described. Both neural and abductive networks implementations are presented and compared. An abductive network three-member committee was developed on data for three successive years and evaluated on the fourth year. Compared to a monolithic model trained on the same full three-year data, the committee reduces the mean absolute percentage error from 2.52% to 2.19%. The corresponding reduction in the mean of the absolute error from 70 MW to 61 MW is statistically significant at the 95% confidence level.

05•02089 Influence of a TCSC in the behaviour of a transformer differential protection Arrieta, M. A. Z. et a[. Electric Power Systems Research, 2005, 74, (1), 139 145. In the last years, a large number of studies have been made on Flexible AC Transmission Systems (FACTS) with the purpose of facilitating their incorporation into the power system. Because of the many