The paper, “Analysis of Flipped Secant Inverse Hyperbolic Pulse-Based FIR Filter for WCDMA” by A S Kang and Vishal Sharma, deals with data communication using pulse shaping techniques. Pulse shaping filters are used in digital wireless communication to shape the signal spectrum and avoid interferences. The analysis of flipped secant inverse hyperbolic pulse-based FIR filter used in Wideband Code-Division Multiple Access (WCDMA) is carried out using MATLAB program. The effects of various parameters like roll-off factor, group delay and interpolation factor on the performance have been studied.

Adders are the basic elements of many VLSI systems and are used in various arithmetic operations. Reducing the power consumption and delay in adders is a very important goal to be achieved in the design of VLSI systems. In the conventional approaches for power reduction like reduction in the power supply voltage, load capacitance or node transitions, various disadvantages like current leakage there are. The paper, “An Energy-Efficient Full Adder Design Based on Energy Recovery Gates and Multiplexer Architecture”, by Manoj Kumar, Sandeep K Arya and Sujata Pandey, deals with the design of a single bit full adder-based CMOS 0.35 µm technology. The proposed adder with multiplexer-based architecture gives a low power dissipation.

The paper, “Failure of 220 kV Overhead Power Transmission Line Due to Lightning”, by T V Gopalan and Niyas Thayyil, describes the analysis of transmission line outage due to decapping of a unit of an insulator string and falling of conductors, and suggests remedies.

Load flow or power flow study is a basic study frequently performed in the planning and operation of power systems. In the paper, “A Comparative Study of Three Load Flow Methods”, the authors, R P Sharma and A K Wadhwani, make a comparative study of the various load flow analysis methods and present a new constant Jacobian matrix method. The proposed method exhibits better convergence reliability. Numerical results from IEEE and other system examples are presented for better future planning purpose.

The paper, “Differential Evolution-Based Algorithm for Congestion Management in a Deregulated Environment”, by R Rajathy, R Gnanadass, K Manivannan and Harish Kumar, deals with the problems faced in a restructured electricity market environment where the transmission network operates at or beyond one or more transfer limits. The transmission system gets congested, resulting in an increase in the cost of electricity, leaving the system security in danger. Congestion can be relieved by rescheduling of generators, on-load tap changers, etc. The selection of generators to reschedule their output for effective management of congestion is a crucial task for the system operator. To relieve congestion, the paper presents a differential evolution-based active power flow contribution factor method for the selection and rescheduling of active power output. The generators to be rescheduled are identified based on active power flow contribution factor using power flow tracing algorithm. The congestion cost is minimized using differential evolution optimization technique. The proposed method results in lesser number of generators participating in the process of rescheduling, thereby reducing the congestion cost to a larger extent. The proposed algorithm is illustrated on an IEEE 30-bus system for inter- and intra-zonal congestion management.

The operation of power transmission line is constrained by limitations of one or more network parameters and operating variables. Flexible AC Transmission System (FACTS) devices like Thyristor-Controlled Series Capacitor (TCSC), Thyristor-Controlled Phase angle Regulator (TCPR), UPFC, etc., are used to regulate the bus voltages and line impedance rapidly and flexibly. The Unified Power Flow Controller (UPFC) is a FACTS device that can control all the three system variables, namely, line reactance, magnitude and phase angle difference of voltage across the line. The performance of UPFC depends on proper control setting, achievable through a power flow analysis program. The paper,“A Comparative Study of 5-Bus and 14-Bus Systems with UPFC: A Power Flow Perspective”, by Ch. Chengaiah and R V S Satyanarayana describes a method to control the settings of UPFC through a modified Newton-Raphson-based load flow calculation. The proposed method keeps Newton-Raphson Load Flow (NRLF) algorithm intact and needs little modification in the Jacobian matrix. Case studies are performed on IEEE 5-bus system and 14-bus system to observe the effectiveness of the proposed method.

-- MSR Murty
Consulting Editor