In the paper, "Application of Particle Swarm Optimization Technique to Alternator Design", by V P Sakthivel, R Bhuvaneswari and S Subramanian, Particle Swarm Optimization (PSO), a population-based stochastic optimization technique, is used for alternator design to minimize the material cost and regulation and to maximize the efficiency. The design of an alternator for maximum efficiency or minimum cost is considered a constrained optimization problem. The design is optimized using three different objective functionscost, regulation and efficiency. To verify the consistency, the proposed method has been applied to two sample alternators, and it is concluded that the cost-based optimum design leads to lower cost of raw material used and this approach will result in acceptable design.

The Power System Stabilizer (PSS) is used in the excitation system of a generator to improve the dynamic performance of the power system. The PSS uses auxiliary stabilizing signals. The application of PSS can help in damping out rotor oscillations and improving the system stability. To improve the PSS design, various control techniques like adaptive control and self-tuning control are adopted. A Ragavendiran, R Gnanadass and M Arounassalame study the PSS system on a Single Machine Infinite Bus (SMIB) system in their paper, "MATLAB/Simulink-Based Modeling and Operation of Power System Stabilizer". Various power system conditions like light, nominal and high load and fault are considered for the simulation study. The transient variations in synchronization parameters, such as speed deviation, field voltage and rotor angle are analyzed to show the improvement in the system performance and stability in various frequency bands.

After the deregulation in the power market, Distributed Generation (DG) is being widely considered. The generating units of limited size (100 MVA or less) are connected directly to distribution network or the consumer sites in the DG system. The paper, "Adequacy Assessment of a Distribution System Having Distributed Generation (DG) Under Extreme Probability Distributions", by L D Arya, Atul Koshti, A K Ganguly and Rizwan Sheikh, deals with distribution systems having DG sets. The capacity reliability evaluation of a composite distribution with customer-owned DG sets is analyzed. Monte Carlo simulation with extreme distributions for load and capacity has been considered and worst case reliability evaluation carried out. The effect of distribution generation has been investigated for system adequacy assessment. The procedure presented in this paper can be used to plan DG required to attain the desired level of reliability.

Reduced-order models are often required in the analysis and synthesis of high-order complex systems to reduce computational time and memory requirements and also for online applications. In the paper, "Reduced-Order Model of Disk Drive Read System Using Hybrid Method", the authors P Munaswamy and R V S Satyanarayana propose a new hybrid method for the reduction of high-order, linear time-invariant system. They consider detailed mathematical model of a disk drive read system and generate a lower-order stable model using a hybrid method based on the Pade approximation technique and the Routh-Hurwitz array. The reduced-order model transfer function gives a transient response matching with that of the detailed model. This method guarantees stability of the reduced model when the original system is stable.

In the paper, "Single-Phase AC Voltage Regulator Using AC Chopper with Series Transformer", by the authors Anoop Mathew, N O Gunasekar, D Bensiker Raja Singh and S Uma Mageswaran, a novel step-down AC voltage regulator scheme using AC choppers is proposed. To verify the performance of the proposed scheme, detailed experiments are performed on a 20 kVA series compensated single-phase AC voltage regulator scheme using an AC chopper with a series transformer. The experimental results indicate that the proposed AC regulator offers good performance and the scheme can be extended for power saving purposes. It can also be used as an automatic voltage regulator or power line conditioner with input transformer and slight modifications.

The development of nano dielectric materials that can be used in capacitors is presented in the paper, "Dielectric Properties of Recycled Poly (Ethylene Terephthalate) (rPET) Composites with Nanoclay Fillers", by S Rajarajan and J Raja. Nanocomposite materials are produced from recycled PET regrinds used as the matrix and organically modified Montmorillonite (MMT) clays as the filler. The authors study the effects of clay content and clay type on sample resistivity and dielectric properties. The specimens were prepared to verify the dielectric properties of the samples by conducting tests for dielectric strength, permittivity and arc resistance, and results presented.

-- MSR Murty
Consulting Editor