Nash equilibrium bidding strategies in a bilateral electricitymarket

This paper examines bidding strategies in a bilateral market in which generating companies submit bids to loads. A load accepts electricity delivery from the generator with the lowest bid at its bid price as long as this price is not higher than the load's willingness to pay. Necessary and sufficient conditions of Nash equilibrium (NE) bidding strategy are derived based on a generic generating cost matrix and the loads' willingness to pay vector. The study shows that in any NE, efficient allocation is achieved. Furthermore, all Nash equilibria are revenue equivalent for the generators. Based on the necessary and sufficient conditions, this problem is formulated as an optimal assignment problem. Network optimization techniques are applied to calculate NE bid prices for the generators     

A comparison study of the capacitive behavior for sol-gel-derived and co-annealed ruthenium-tin oxide composites

The electrochemical behavior of mixed Ru-Sn oxides fabricated by a modified sol-gel process and a co-annealing method are systematically compared (using cyclic voltammetric and electrochemical impedance spectroscopic analyses), for the application of supercapacitors. Influences of annealing temperature and time on the specific capacitance and textural properties of oxides are also studied. Based on the quasi-linear dependence of voltammetric current density on the scan rate of CV (from 25 to 500 mV s⁻¹), the lowest proton diffusion resistance, and the high-frequency (∼426 Hz) capacitive responses of the co-annealed composite (RTOC_co) as well as its ease in composition control, co-annealing of hydrous RuO₂ and SnO₂ at 200 °C for 2 h is recommended as a promising and practical method for preparing mixed oxides in the supercapacitor application.     

Electrochemical catalytic modification of activated carbon fabrics by ruthenium chloride for supercapacitors

A novel method, electrochemical catalytic oxidation via a ruthenium redox couple in an aqueous RuCl₃ · xH₂O solution rather than the anodic deposition of Ru oxides, was developed to modify the microstructure and electrochemical properties of activated carbon fabrics (ACFs). The variation in microstructures (i.e., specific surface area and mean pore size) for the modified ACFs was examined by means of nitrogen gas adsorption isotherms. The distribution of oxygen-containing functional groups within the modified ACFs was identified by temperature programmed desorption (TPD) and X-ray photoelectron (XPS) spectra. Effects of the electrochemical catalytic modification on the electrochemical characteristics and reversibility of ACFs were investigated systematically by means of cyclic voltammetry (CV) and chronopotentiometry (CP) in 0.5 M H₂SO₄. The total specific capacitance of ACFs reached a maximum (ca. 180 F/g measured at 10 mA/cm²) when they were catalytically modified at 1.15 V with a passed charge density of 5 C/cm². These modified ACFs were demonstrated to be an excellent candidate for the supercapacitor application.     

Web-based tutoring in power engineering

This paper deals with the application of web-based technologies to power engineering education in an interactive student/mentor environment. The modern teaching/learning concepts and new technologies to support these concepts have been developed. This project incorporates web-based tools, including Internet, videoconferencing, and educational intelligent system modules for power engineering education. Different student learning styles are adapted for power engineering applications. The proposed interactive learning environment allows the mentor and students to best utilize the facilities for effective teaching and learning.     

Learning to recognize vulnerable patterns due to undesirable Zone-3 relay operations

Undesirable zone 3 relay operations caused by unexpected loading conditions can contribute to the cascaded events, leading to catastrophic outages. Identifying the basic patterns of zone 3 relay operations in advance is an effective way to help prevent cascaded events. The postcontingency impedances seen by zone 3 relays can be calculated on line in a steady state security assessment framework. However, their accuracy is inadequate compared with the postcontingency apparent impedance obtained from off-line time domain dynamic simulations. This paper proposes a fuzzy inference system (FIS) to correct discrepancies between the postcontingency apparent impedances obtained from the results of steady state security assessment and the corresponding values obtained by time-domain simulations. The postcontingency apparent impedances obtained from the results of steady state security assessment can be corrected on line using correction terms provided by the FIS. The dynamic model of a 200-bus system is used to validate the performance of the proposed FIS. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Electrochemical and textural characterization of binary Ru-Sn oxides synthesized under mild hydrothermal conditions for supercapacitors

Hydrous ruthenium-tin oxides (denoted as (Ru-Sn)O₂·nH₂O) were synthesized under a mild hydrothermal condition. The mean particles size of pristine RuO₂·nH₂O, smaller than 3 nm, was decreased with the introduction of Sn into the precursor solutions while it is not significantly affected by varying the Sn content. The textual characteristics of (Ru-Sn)O₂·nH₂O were analyzed through means of X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), electron diffraction, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analyses (TGA). From the ideal capacitive behavior of pristine oxides with the Ru content ≥40 at.%, hydrothermal synthesis favored the formation of hydrous oxides with a novel structure providing excellent pathways for electron hopping and proton diffusion/exchange during the charge storage/delivery process. The introduction of tin oxide was demonstrated to successfully promote the utilization of oxyruthenium species, reaching a maximum C_S,Ru of ca. 830 F/g for pristine Ru_0.6Sn_0.4O₂·nH₂O (measured at 25 mV/s).     

Developing the dual system of wind chiller integrated with wind generator

The successfully developed wind chiller in our CCT Lab. directly uses wind force to drive refrigeration system and hence reduces two times energy conversions between mechanical and electrical energies. The wind chiller needs high wind speed for its effective work due to the large working torque is required by the compressor. For the purpose of enlarging the applied wind field by the wind machine, this work aims to develop a dual system of wind chiller integrated with wind generator. The integrated wind generator can use the wind energy which cannot effectively drive the compressor. Therefore, the new developed dual system can apply larger range of the wind field and further increase the total working efficiency of the wind machine. A programmable logic controller (PLC) is applied in this wind forced dual system to select the wind chiller or the wind generator separately in terms of the rotational speed of the wind machine. In this work, the wind chiller is switched on while the accelerated rotational speed reaches 80 rpm and off while the decelerated rotational speed reaches 60 rpm. The integrated wind generator is switched on while the decelerated rotational speed reaches 60 rpm and off while the decelerated rotational speed reaches 40 rpm. The two apparatuses in the dual system always work separately. The results show that there is ca. 18.5% increment of effective working efficiency which is captured by the wind generator.     

Steady-state voltage stability regions of power systems

This paper deals with the steady-state (small-disturbance) voltage stability of power systems. A simple example is proposed to interpret the real-world phenomena of voltage instability. For general interconnected power systems, the voltage stability is studied via linearized dynamical equations of on-load tap changers and steady-state decoupled reactive power flow equations. A set of conditions is derived for a hyperbox of tap settings and load bus voltages to satisfy the steady-state stability requirements. The results can be used to construct steady-state voltage stability regions for the security monitoring of power systems.     

Voltage instability: mechanisms and control strategies [powersystems]

One of the main objectives in operating an electric power system is to maintain a proper voltage level throughout the system. Failure to do so can lead to equipment damage and blackouts. The article discusses the nonlinear aspects of power systems, with emphasis on voltage instability. It provides an overview of the state-of-the-art on the analysis and control of voltage dynamics. Dynamic mechanisms and control strategies are discussed from both theoretical and practical standpoints. The remedial controls implemented in the Puget Sound region of the Pacific Northwest indicate the practical significance of the research area