06 Electrical power supply and utilization (scientific, technical)

reactance order. ThiL reactance order IS converted into the corresponding firing angle of the TCR through a look-up table. llowevcr. in most case\. this controller I\ designed heurIstically and there I\ no ~uarantec that such a control law will provide a global stability. In this paper. the characteristic of this device is used to obtain a linear, discrete-time state space model of a TCSC-compensated transmission line. This model is derived in the d-9 axis domain. Three different controllers are designed bated on this model. two of which are used for regulation and one for power tracking. The model and the controllers are validated through digital computer simulation studies.

OOlOO816 Molecular orbital calculations on lithium absorption in boron-or nitrogen-substituted disordered carbon Kurita, N. Carhor~, 2000, 38, (I), 65-75. In order to clarify the reason why, horon-suh\tituted disordered carbons can store more Li atoms than pri\tlne carbons. several polyaromatic hydro- carbons have heen employed as model clusters for disordered carbons and investigated the effect of horon and nitrogen substitutions on the stable structures and electronic properties of model clusters, by using a semiempirical molecular orbital method. Boron substitution creates an electron acceptor level in a lower energy region than that for the pristine carbon. This lower acceptor-level accepts electrons from the absorbed Li more easily, so that the Li absorption energy for the boron-substituted cluster is much larger than that for the pristine carbon. On the other hand, for the nitrogen-substituted cJu\ters, the electron acceptor level is almost the same as that for the pristine carbon, so that the Li absorption energy is not enhanced by nitrogen-substitution. These results suggest that the larger Li-storage in boron-substituted disordered carbons is related to the creation of a lower acceptor-level caused by boron substitution.

00100817 A multifunctional energy-storage system with high- power lead-acid batteries Wagner, R. ef crl. J. Poww Sowces, 1999. 78, (l-2), 356-163. A multifunctional energy storage system is presented which is used to improve the utilization of renewable energy supplies. This system includes three different functions: (i) uninterrupttble power supply (UPS); (ii) improvement of power quality; (iii) peak-load shaving. The UPS application has a long tradition and is used whenever a reliable power supply is needed. Additionally, nowadays. there is a growing demand for high quality power arising from an increase of system perturbation of electric grids. Peak-load shaving means, in thic case, the use of renewable energy stored in a battery for high peak-load periods. For such a multifunctional application large lead-acid batteries with high power and good charge acceptance, as well as good cycle life are needed. OCSM batteries. as with positive tubular plates and negative copper grids, have heen uwd successfully for a multitude of utility applications. Thi\ paper gives two examples where multifunctional energy storage systems have started operation recently in Germany. One system was installed in combination with a I MW solar plant in Herne and another one was installed in combination with a 2 MW wind farm in Bocholt. At each place, a I.2 MW h (I h-rate) lead-acid battery has been installed. The batteries consist of OCSM cells with the standard design but modified according to the special demand of a multifunctional application.

OOIOO818 A multi-layered approach for absorptive glass-mat separators Ferreira, A. L. J. Power Sources. 1099, 78, (l-2), 41-45. The traditional method of manufacturing absorptive glass mats (AGMs) for valve-regulated leed-acid (VRLA) batteries is to hlend two or more types of fibres together in an aqueow acidic solution and deposit this blend on to either a moving endless wire or a rota-former (another version of an endless wire). The sheet acquires consistency as the water is withdrawn; it is then pressed and dried against heated drums. The methods of fibre dispersion and deposition can be changed so that the different constituent fibre types of an AGM separator are processed separately in distinct and separate layers. This fibre segregation results in the enhancement of some key characteristics of the separator and thus brings some very definite advantages to the performance of VRLA batteries, e.g. the ability to deliver higher currents at higher discharge rates. Also, important AGM character- istics. such as wicking, porosity/pore-size and stratification, are radically modified by adoption of the multi-layered AGM design. As a consequence, the high-rate and cycling performances of VRLA batteries are equally affected.

00100819 Nanostructured tin for use as a negative electrode material in Li-ion batteries Whitehead, A. H. ef (11. J. Power Sources. 1999, 81-82, 33-38. A series of mesoporous tin samples have been prepared by means of a liquid crystal templating method. TEM images and X-ray diffraction data show the mesoporosity and the scale of the repeat structure. The lithium insertion and extraction hehaviour of liquid crystal templated films was compared with those obtained from non-templating electrolytes. It was found that the templated films showed higher extraction capacities, which were attributed to the ability of mesoporous tin to expand and contract with less structural degradation than nonporous tin.

00100820 New control strategy for shunt power conditioners Lu, C. W. Elecrric Powr .Swtrms Rewrch. 1999, 51, (2), 103-108. The proliferation of nonlinear loads has resulted in the need for active solutions to curb the effects of harmonica pollution. Shunt power conditioners are widely used but with conventional control strategies, the

performance under practical nonideal supply conditions requires improve- ment. A novel control strategy (synchronous power flow) for three-phase systems is proposed to achieve robustness in the presence of supply distortion and unbalanced loads. Two critical aspects are investigated: harmonic components detection and control of instantaneous power flow. Both harmonics compensation and power factor correction qualities are analysed and compared with existing strategies. Superior performance from the proposed scheme has been verified by simulation case studies.

00100821 A new reduced order multimachine power system stabilizer design Aldeen, M. and Lin, L. 114.

Electric Power Sysrem Research, 1999, 52, (2). Y7-

This paper presents a new design method for a multimachine power system stabilizer. The stabilizer is dynamic, low order and robust. The order of the stabilizer can be as low as the number of those machines for which a stabilizer is necessary. The design method is systematic, simple and easy to implement, using standard MATLAB IM functions. A three machine power system is used as a case study. A comprehensive treatment of design and analysis is given.

00100822 Non-conventional fuel cell systems: new concepts and development Zhu, B. et al. J. Power Sources, 79, (I), 30-M. This paper considers fuel cell research from a new point of view. by describing the non-conventional systems including intermediate tempera- ture and new concept fuel cells based on recent developments of materials and systems.

00100823 On charge conditions for Li-ion and other secondary lithium batteries with solid intercalation electrodes Chung, S. K. et al. J. Power Sources. 1999, 79, (2). 205-21 I. The simple model of continuous non-porous electrode was found to provide a reasonable theoretical description for the electrochemical process of lithium insertion into a convenient solid electrode, consisting of active material, fine carbon and binder. of the rechargeable lithium batteries with common liquid organic electrolytes. The model uses only one experimental fit parameter-effective diffusion coefficient of inserted Li that can easily be obtained from galvanostatic charge-discharge data. Approximate simple equations were derived to calculate the charge conditions for secondary lithium batteries. It was shown that charging with linearly descending current results in more than 2.5.fold reduction of charging time as compared to the constant current charging at the same charge depth.

00100824 Optimum load shedding for avoiding steady-state voltage instability El-Sadek, M. Z. ef al. Elecrricui Power Systems Research. 1999, 50. (2), 119-123. The problem of load shedding is addressed in this paper as an emergency means for avoiding the occurrence of voltage instability in distribution and transmission power systems. Optimum locations of loads to be shed are found together with their optimum required quantities. The L-indicator index is used for this purpose with a modified new technique. Applications to a test system are presented to validate the applicability of the proposed new technique to a system of any size.

OOlOO825 Parallel processing application in traction motor fault diagnosis Sen, A. K. and Murty. A. S. R. Elecwic Power Sy.wvn~ Reseurch, 1999. S2, (3), 241-249. Parallel processing-based system condition monitoring and fault detection are the order of the day for providing greater safety and reliability of the system. Fast and accurate fault diagnosis and detection predictor provides better system protection and maintenance planning of spare parts. In this paper, an attempt has been made to predict the temperature profile of different parts of a traction motor by using parallel processing techniques. The prediction of temperature of different parts of the motor during healthy and faulty condition have been established hy developing a thermal model of the machine and transputer based concurrent process predictor has been taken up to assess the thermal hehaviour of the machine The significant advantage of this predictor is its capability of providing early warning about the condition of the machine with greater confidence and built in redundancy and thereby ensured the protection of the machine.

00100826 Performance requirements of automotive batteries for future car electrical systems Friedrich, R. and Richter, G. J. Power Sources, 1999, 78, (l-2), 4-11. The further increase in the number of power-consuming functions which has been announced for future vehicle electrical systems, and in particular the effects of new starting systems on battery performance, requires a further optimization of the lead acid system coupled with effective energy management and enhanced battery operating conditions. In the face of these increased requirements, there are proven benefits to splitting the functions of a single SLI battery between two separate, special-purpose batteries. each of which are optimized. for high power output and for high energy throughput, respectively. This will bring about a marked improve- ment in weight, reliability and state of charge (SOC). The development of special design starter and service batteries is almost completed and will lead to new products with a high standard of reliability. The design of the power-

92 Fuel and Energy Abstracts March 2000